Quote from MrN:
My experience suggests that the "let winners run and cut losers short" idea is often not applicable or useful to day or short term trading. Quite often trying to graft these notions onto a winning edge simply kills the edge, or at best simply reshuffles the payoffs to create more losing trades with less frequent big winners.
If it is a matter of just holding onto winning trades, one thing that can work is to stop looking at short term charts or staring at the quote screen all day. I spend most of the day looking for or evaluating different trading ideas. This is what has worked for me.