I can relate to where you are because I am just now coming out of the tail end of a difficult period of adjustment and negativity.
I agree with Jeff that there is too much focus on finding one purpose in life - be that one idea, or one master goal. The most important thing I ever did with regard to finding my purpose was to froget about other peoples definitions of purpose and their beliefs around purpose (even Steve's).
When I did this I began thinking about what my purpose would feel like - not what it was or what it would be, what it would feel like to have this purpose...
I found that mt purpose would make me feel peaceful and energised at the same time, very still yet with a great reservoir of possibility.
I came up with three things which are my purpose... they all make me feel this way. They are synergistic, and they can be applied or cultivated seperately, giving my a braod range of ays to serve my purpose...
So, my advice to you would be to think about how your purpose is going to make you feel (which will hopefully make you feel better anyway) and then to start looking for things in your life that make you feel that way.
Reply or PM me if I can help in any other way...