[exacube]

I think it's very important to understand and accept that what you are feeling is not a normal state. I would say try to think focus your efforts on arriving at the normal state; of being able to feel pleasure and happiness. Depression is well within the range of human emotion, but you must understand the other parts of the range, and work towards them! As it has already been said, it sounds like what you're feeling is chemical, and you should try to address that -- you can't easily rationalize depression away if its in fact chemical.

BTW, I am very happy to hear that you've been helping the needy and being selfless in general :-)!