You plan ahead of time. Of course, no plan survives contact with the opponent and then you improvise. There is, as you correctly observed, no time for conscio

You plan ahead of time. Of course, no plan survives contact with the opponent and then you improvise. There is, as you correctly observed, no time for conscious thinking then. It's all 'muscle memory' so to speak. Hence you won't be competitive until you have played thousands of games. The match-making algorithm ensures that you win ~50% of the times, unless you're at either extreme of the skill level. Every so often (or quite often) you're matched with a vastly superior opponent and blasted to pieces, but it's already much better than SC1 w/o such match-making, where beginners never saw the light. Also Blizzard has a good handle on cheating in SC2 (unlike SC1).