come to think, I have a non-scientific solution :)
we all know the tribulation of when you buy it moves lower and when you sell it moves higher
when your about to throw in the towel, sell 2 or 3 shares then pps will move up
or buy 2-3 shares of something at first and wait for it to move down before entering the position
believe it or not, as ridiculous as it sounds, it works for me most of the time