In one of my classes I took last semester we studied "Positive Psychology". We were looking for what actually makes qualifies as actual good/useful positive psychology. Positive psychology is a pretty new subject, generally used as a way for people to make money.

You could write a good self-help book. However in my opinion and experience when I am depressed that kind of stuff is not going to help. The best thing for me is to borrow from CBT and try to change what I am thinking in general.

Although, that is easier said than done.