But people with bipolar don't get to choose whether it's a little more or a lot more. That's the nature of the illness. You start with an exciting, powerful, bit of extra oomph, which is narrowly balanced between useful extra capacity to get stuff done on one side and out of control mania on the other. This can last months or years. Sometimes followed by a crash; and the crashes are nasty. (Obviously there are different forms of bipolar, and not all forms follow that pattern.)
(Also, I don't get why you chose to link violent behaviour with mental health problems. People with mental health problems are much more likely to be the victims of violence than the perpetrators.)