As much as I hate it, exercise helps me (when I am able to force myself to go). Once I get to the gym and start working out I feel better. I think aside from the endorphins I also feel a sense of accomplishment when I exercise which can also lift my mood. Socializing can also help - I tend to feed off other people's mood so if I'm with happy upbeat people that tends to rub off on me a bit. Obviously it is not always appropriate to exercise of socialise like late at night and that's when I struggle a lot. Sometimes breathing/relaxation techniques help then.