Some very good advice in this thread. I would only add one thing. Just do not resort to drugs (legal or illegal) in the hopes to improve performance. Drugs like adderall (or even anti-depressants like SSRI's, etc.) might show some benefits, but likely only the short term. By then, you will have trouble getting off, and cessation of the drug will take you back worse from where you started.

Also, you might not be getting enough physical excercise. Probably the best anti-depressive/stimulant there is.