All you need is an IDEA.
I know you have the same feeling as I have: whenever I sell a stock because it does not perform, it often turns out that It begins to take off after you sell it. I've seen it many times and heard many times from my friends, as if the market is a calculating machine that works against you. In a way, it is. But mostly, it's because we are human beings, and we want quick profit, and we lose patience very easily. Many of my holdings turn out pretty well because I hold them long enough. Just like you find a gem in a debris of garbage: at the beginning it looks ugly and stinky as the other garbage in the debris, but with time, when other people start to realize it is a gem, they will do the polishing for you. And with the polishing, still more and more people realize it's gem, and there comes your payoff. But of course, that takes time; and, more importantly, you have to convince yourself that the garbage you found is indeed a gem. This requires a discerning and well-trained pair of eyes and a lot of patience. Do both well, and you will get rewarded.