"And, at any point in time, the richest traders are often the worst traders. This, I will call the cross-sectional problem: At a given time in the market, the most successful traders are likely to be those that are best fit to the last cycle. This does not happen too often with dentists or pianists-because these professions are more immune to randomness."
~ N.N. Taleb
Trading is a funny game. You can do everything right: research your assumptions thoroughly, wait for the perfect technical entry, size the position correctly, and even successfully exit before price starts to turn. But unfortunately, this still doesn't guarantee you'll have a good year. Successful process execution only ensures profits in the long-run. Anything can happen in the short-run.
The opposite is true as well in the case of undeserved windfall profits. You can pick a stock based purely on "gut feel", plow your entire