I can't speak for anyone else, but I know I personally have mental health issues including major depression. A lot of times poker was the only thing that kept me from doing something stupid because it acted as a distraction from my feelings. While I was playing poker I could focus entirely on that and not how I was feeling at the time. This lead to many banged desks, choice yelled words and thrown objects.
For anyone with that problem, get help. It took me 20 years, but I eventually found a doctor and a set of meds that completely took away my symptoms. The key for me was saying, "screw side effects, I'm going to stick with a set of meds no matter what." Now, even the worst bad beats in the most important games just result in a "well, that sucked".
If you need help, look for help. It can work . . . eventually.