Pets are mental health barometers
I'm not very good at telling when I need more sunlight, exercise, or even food. But I can tell when our pet needs things, and find it pretty motivating to take care of them (and hence myself).
Cats gave my son a reason to stop drinking and go home at night. He cared for them when he couldn't care for himself. Without them i don't know if he would still be here.
This is, in large, why emotional support animals exist.
Rule 2: Treat yourself like someone you’re responsible for helping.
At one point, years ago when I was so depressed I could barely get out of bed, I realized "If someone treated a dog the way I've been treating myself, I would take steps to get that dog taken away from them." Food every day, water several times a day, walks, baths, interaction, play.. I was doing none of these things. It really helped to try to think of myself as an "other" that needed care.
Rule 1: Do not act incautiously when confronting little bald wrinkly smiling men!
That is true if you possess the ability to empathise, some people treat their pets as accessories. Mine live better than I do lmao
Personally, I found it already helpful to force myself to go for a walk every few days. In my case, I was able to get rid of my car, so now grocery shopping is my mandatory walk.
And the weirdest part is that I'll now sometimes want to go grocery shopping, even though I still have plenty food at home. I think, after doing it for a while, my brain understood that the being miserable part isn't normal/necessary and that the walks do make that better.
I have a lot of pets and caring for them is my passion. That's part of why I have so many. Caring for them is self-care for myself. It makes me feel good. I have two dogs, two cats, and 10 ducks. I have a few jumping spiders living inside my house, but they're not pets. Just guests that help me get rid of any other bugs.