Besides the obvious things such as exercising (I do forest runs)/ walking more regularly and often, a dog has had a calming and stress reducing effect on me I'd never have imagined possible.
I have ADHD and besides the impulsivity that comes with it, it was untreated until after I adopted my dog. Even prior to diagnosis, having a mammal besides you that you cannot talk to, but that is very reactive to your emotions has calmed me down significantly.
I experienced I can only interact calmly and trusting with my dog if I am, in fact, doing so being calm and trusting myself.
Also, dogs are amazing at executive functioning. They don't fret past mistakes, they try again. Seeing it physically in front of you every other day puts me in a different mental spot. Can't be depressed if I see it's possible.
And last but not least, I've never had so many positive random interactions with strangers ever in my entire adult life.
Both me approaching others when my dog is with me or being approached.
People just don't read you as a creep or threat if you present yourself as being able to interact well with a dog.
I have had fish and ants before, the mental and social effects don't ever compare.
Highly recommend adopting a dog if you're so inclined.
It's awesome.