You can refill your mental health by going for walks and talking to your bot. You will have to do it a fair amount because the mental health only goes a tiny bit when you do them. Also later on in the game there is a drug that says it will help with your mental health but i don't recommend them.
I don't recommend the drugs because when they are available they say that you will get addicted. I don't know the full outcome of using them because I haven't tried them yet but I assume it's not good.
