From Art of War:
1. Sun Tzu said, The good fighters from old first put themselves beyond the possibility of defeat, then waited for an opportunity of defeating the enemy.
I like to think of this in a few ways.
a) Putting oneself beyond the possibility of defeat means having some type of stop. It could be an emergency stop, a mental stop, a timed based stop. Also, it could mean having a loss limit for the day. Therefore even if you lose a battle or more, you are not defeated.
b) The other way, I take this to mean waiting for your setup in which you have a high probability of victory.
Sun Tzu said, he who wins his battles makes no mistakes. I believe this to mean that when you are trading, you make sure that before and when you take the trade, that it is based on your edge and not on other factors.