Here's a little tidbit that may actually play into the testosterone increase/decrease after workout thing.
Men who feel they have "won" have a testosterone spike. Men who feel they have "lost" have a testosterone dip.
Actual winning or accomplishment has no effect, simply the belief. So, it could very well be that the more you feel, "That was an awesome workout, damn I'm awesome, I rock!" at the end of a workout, the more testosterone you produce (and thus the more gains you're likely to make) and the more you think, "Damn I'm so far from where I want to be, fuck I suck." the less you'll make testosterone and the more you'll inhibit your progress.
Hormones and bodies are strange and complicated things, even for us biologists.