I have found that changing my thought patterns has been a major factor in overcoming issues like depression, suicidal feelings, negative thought patterns, etc. Having grattitude has also been very helpful... it's hard to feel depressed during moments when I'm feeling thankful - they just don't really go hand-in-hand.
As for helping others... we actually gain quite a bit by giving to others. Sometimes we're too tired or drained or negative to realize this, though. And sometimes we give to others because we don't feel that we deserve to give to ourselves... in those situations, we sometimes feel angry because we wish someone would give to us what we give to others. We just have to work on accepting and loving ourselves and then we become more open to the postives that come our way!