Sometimes, I don't. The things that I notice when I lose or play poorly is that I am often pissed or just have lost - "tilt" if you will. When I'm in a rush and need to get back to doing something else, I don't focus and I play poorly (I was in three tournaments today and I played poorly in many of them because I didn't realize they all had overlapping start times....)
So, SC2 is not just what you know, or how fast you can execute it, but your mood plays a strong component, it seems, in your gameplay as well.
If nothing else, I think that's a good lesson for the day.