When you are getting beat to death, get your head out of the mixer.
You should always have a worst case point. The only choice should be to get out quicker.
When things aren't going right, don't push, don't press.
Trading decisions should be made as unemotionally as possible.
When you have a position, you put it on for a reason, and you've got to keep it until the reason no longer exists.
I learned to avoid trying to catch up or double up to recoup losses. I also learned that a certain amount of loss will affect your judgment, so you have to put some time between that loss and the next trade.