I think nightnurse is right, although I would love to be proved wrong (I'm still waiting for the University at Buffalo authors to come out with a large-scale, definitive study showing that controlled exercise, say for 20 mins a day, can help improve symptoms - for now I'm skeptical).

I believe my most significant setback came from overexerting myself about two weeks after my concussion. Over the course of a single day, I went for two walks outside, had a long phone conversation (about an hour), socialized with family for an hour and a half, and hoisted and carried my 45-lb nephew several times. The next night and day I felt really bad, and that was when my tinnitus started. I think the lifting was the main culprit - although I didn't feel the effects immediately, I think it really overtaxed my recovering brain at the time.

My advice would be to start with a baseline of as close to complete rest (mental and physical) as possible, and incrementally add activities as you progress. Think long term, not today or this week or next week. Be patient, and take good care of yourself (rest, nutrition, relaxation techniques, social support, etc).