Some years ago, my combat-related PTSD hit me. This bit from Paul Simon's "Slip-Slidin' Away" fit:

She said, "A good day
Ain't got no pain"
She said, "A bad day's when I lie in bed
And think of things that might have been."

One of my dogs, Belle, would lie down with me on bad days, giving me loving care. She knew I was hurting, and did her best to help. I got more help from her than from the VA shrink I saw. At that time, this man's best friend was his dog.

A year or so later, Belle got sick and had to be put down. I held her when the vet gave her the injection. I owed it to her.

Another dog, Madison, liked to get into bed with my wife and me, and have me rub her throat. When I did that, she purred. I've never known any other dog who purred. She stopped doing that after a couple of years. Madison got an aggressive cancer, and on the morning we were going to take her to the vet, she got back in bed with us and purred. She then got off, laid down and died. She was telling us "adieu".