If have flipped a coin 40 times and it has come up heads 35 times, what are the odds that its heads the next time? It's 50/50, the next flip isnt dependant on the last, and is should be looked at in the context of all the coin flippings that have occured whether you did it or some-one else did. Over time you can apply your edge, but I think that each trade is pretty much a random event. If I'm long Yahoo, how much control do I have if a hedge fund manager who is long 2million shares wants to get out at the market? I have no idea why that would happen, but its not 100% impossible either. I think a lot of the trouble people have comes from not understanding that, one trade is just that, one trade and anything can happen. Its only over time that you can press whatever edge you might have.
Brandon
ps, "luck" might not be the best word to describe it, but I don't know what other word to use to describe it.