The day with my beloved Diesel started like any other—he slept in while I started the coffee and logged onto work. We went for our morning stroll and I came back to feed him, but when he didn't immediately devour his bowl as he does every time, I knew something was off.

Making a mental note, I started monitoring his behavior throughout the day. He seemed like his normal self. But when dinner came along and my Chow Chow mix didn't eat again, it cemented my husband's and my concerns.

Diesel had been retching, his stomach bloated, and he looked uncomfortable. I couldn't rest that night knowing something was off, prompting us to rush to the animal hospital at 10 p.m.

However, the night at the emergency vet didn't come with immediate answers. Instead, I was given two possibilities: valley fever or cancer.

I couldn't wrap my head around it. Only a few weeks earlier, Diesel, my fluffy and, albeit biased belief, cutest dog ever, had his regular vet visit. His tests and bloodwork came back healthy. No sign of concern.

The emergency vet told us Diesel's symptoms sounded like valley fever, but he would still run other tests. That surprised us as new Arizona desert dwellers originally from the Northeast. We didn't know anything about valley fever.

Valley fever is a dust-borne fungal infection commonly found in the Southwest. The American Kennel Club (AKC) reported dogs could breathe in the fungal spores, which can lead to severe illness. They might develop a respiratory infection. Symptoms include lethargy, coughing, fever, loss of appetite, weight loss, and weakness or lameness.

To rule out other possibilities, the vet took X-rays, which revealed something else entirely—a mass around Diesel's heart base. He didn't immediately say it was cancer, wanting to get the test results back first, but a week later, we got the call to confirm. It wasn't valley fever. Our 12-year-old boy had cancer.

We followed up with our regular vet the next day where she talked us through this type of cancer—Hemangiosarcoma. Known as the "silent killer," hemangiosarcoma is a highly invasive canine cancer that causes blood vessels to branch, fragment or rupture. Dogs often show no symptoms until the tumor grows large enough to rupture and spread, which is oftentimes too late to save the dog's life.

About 300,000 dogs die because of hemangiosarcoma in the United States annually. This number represents between 5 and 7 percent of the nearly 6 million dogs diagnosed with cancer each year.

Diesel's mass grew so large it started to push on his trachea, causing his retching. The vet gave him 20 days left to live, the average time she said she sees dogs last with this type of cancer.

Tears immediately streamed down my face. How could this be? What have I missed? We give him all the right food. We give him added supplements. We walk him at least an hour every single day. Rain or shine. How is this fair?

Factoring in the week it took to get test results and looking back to when he might've started showing signs, we figured maybe Diesel had a week or two left. Although he's had a beautiful, healthy and fulfilled 12 years, it came too fast. It felt like we barely had time together.

Our vet walked us through the potential outcomes of what would happen as the cancer progressed. Diesel could bleed out internally, possibly suffocating on his blood, or the sac around his heart would fill with fluid that would eventually make it stop beating.

Both sounded painful and something neither of us wanted to experience, let alone put Diesel through. That's when we decided to call it before he became too uncomfortable or unrecognizable.

When Is It Time?

Deciding whether it was Diesel's time or not was impossible. We toyed with the decision during his final days. He had moments where he looked like a young pup and we thought we shouldn't. But deep down I knew he was only holding on to ensure we would be fine without him. He was ready.

I was lucky enough to be granted time off from work and spent the last few days with him. We squeezed in park hangs where he rolled in the grass, one of his favorite activities. He wasn't the biggest cuddler, but we snuck some of those in and made sure our two cats, Willow and George, got time with him too.

They truly looked at him as a big brother, always rubbing up against him. Although, they were a bit too fast for him when it came time to play. He would whine as if he felt left out.

Then, of course, we ordered all his favorite foods—pizza, McDonald's and pup cups—to treat him on his final days.

It's hard not to think about what I could have done differently or why I didn't notice anything sooner. But I have to think back at all he did do during his 12 years after being rescued as a pup.

When Diesel was about a year old, my husband noticed him tied to a tree in someone's yard day in, day out. Winter approached and he couldn't stomach Diesel alone outside. When the first storm hit and Diesel was still outside, he confronted the owners. They agreed to let him take Diesel.

He was skin and bones. A scar from being tied up ran from his neck down his back. Diesel immediately hopped into the car as if he knew he was saved.

Diesel didn't care where he was as long as he was with one of us. From college in upstate New York with my husband, to city life in Philadelphia when I came into the picture, Diesel came with us during every move.

When my husband started travel nursing, Diesel was right there with us, in the middle of our front seats, ready for the next adventure wherever a contract took us next. He earned himself the nickname Van Diesel after we lived in a camper van as we traveled between contracts.

Diesel loved hiking and walking to coffee shops to get a treat. The workers always knew his name before learning my name, as it should be!

He started to love the water and ocean in his senior years, although, he never went past his waist. He knew his fluffy tail was his best feature and didn't want to get it wet.

At-home Euthanasia

Knowing Diesel gets anxious at the vet's office, we decided to have an in-person vet come to our house in Arizona. We wanted him to be surrounded by our belongings, our smells and us.

I didn't know what to expect, but she walked us through what would happen. He would receive two injections—one to sedate him so he could relax and the other was the euthanasia solution. We stayed with him through every step of the way. He felt our love to the very end.

The tears never stopped as I held his paws and told him he would no longer be in pain. Even after a million kisses, I would do anything to have one more.

Many might not believe me on this, but the moment he took his last breath, I heard birds chirping outside. It sounds ridiculous, I know, but I'm positive those chirps were a sign letting me know he was getting carried up to doggy heaven. He was letting us know he was going to be OK.

Navigating the Decision

Grieving is inevitable when it comes to pet ownership. As much as one doesn't want to think about that horrible day, it comes. And when I say it hit me like a ton of bricks, I'm not exaggerating.

Diesel was my first dog. He was my unofficial emotional support dog who was there with me through life's ups and downs.

Jennifer Scanlon, a social worker with VCA South Shore (Weymouth) Animal Hospital, spoke with me about pet grief and how she helps others navigate difficult times.

"When the quality of life is impacted that is usually when we want to decide and think about euthanasia," she said. "...These decisions are so heavy. That's the disadvantage of not having pets telling us it's time."

Scanlon shared there are several different factors that could affect a pet's quality of life. Perhaps it's physical—weight, sleeping too much, how they're eating and drinking. Owners could also look at how pets interact with them. Are they responding to your presence? Are they interacting the same way they have before?

Because there is such an emotional attachment to this decision, Scanlon suggested writing it down as sometimes it helps people think more logically. It separates the emotion.

It's normal to feel conflicted and divided about making this decision. In her experience, she's seen that families are more guilty of waiting too long than making the right decision.

Scanlon said they typically recommend euthanasia when it's nearing a pet's life because it gives the owner "a little more control." It sets a plan and allows the owners to be there. Plus, it avoids the possibility of your pet not having to go through a scary experience.

"It is very rare for pets to die peacefully," she said. "[Euthanasia] takes away that pain and anxiety of that and the anxiety for you as well."

Scanlon stressed that this decision doesn't take away love. Instead, this is love and kindness.

"Ultimately, it's hard because the relationship with our pets is so profound and so deep," she said. "They become family members."

Working Through Pet Grief

There is no one-size-fits-all for grief. No instruction manual on how to ease the pain. Some might avoid it because they know how painful it can be. Maybe they don't have the capacity to grieve.

I was down hard for the first few days, unable to get myself out of bed. I think it will always hurt, but it's getting easier. I'm learning that it comes in waves.

"Every person has different coping mechanisms, life experiences, love and attachment to pets," Scanlon said.

She added that pet grief can be very isolating, especially since it isn't always looked at the same way as human loss. It's more than alright to give yourself time. Scanlon said it could take months or years to process the loss.

Sometimes pet grief isn't just for the pet. It can be for the identity you had with your pet. You might've had a routine walking your dog around the block. You've become known in the neighborhood because of your dog. You were your pet's caregiver. Losing your pet means also losing these identities.

There wasn't a time I walked Diesel without someone commenting—"look how fluffy," "he's so cute," "omg is that a bear?" I miss how he made strangers smile. I miss seeing how much he can make a person's day.

Scanlon runs support groups for those who are grieving after their pet passes. A big part of these sessions includes navigating the new normal. These groups help others realize they are not alone in this feeling. It is a safe space where people aren't going to minimize your loss.

But if you are not comfortable joining group sessions, there are other ways to help with the grieving process, such as books, websites and podcasts.

"I do think that ultimately pet loss is so difficult and I don't think that if you lose a human or pet you ever get over grief," Scanlon said. "I do believe over time the intensity will lessen but the grief will remain with you."

Tears always fill my eyes as I remember my boy. But a friend's words stuck with me and keeps me going: "I bet he's making everyone jealous in doggy heaven with all of his stories."