Markets are all about buying and selling, and the market itself will happily let you know if your strategy, your tactics, your rules and your intuitions are up to the task. But year in and year out, the lesson the market is fondest of teaching is about selling. I know, I know, you’re probably weary of investing experts who always want to talk about when to sell. It’s the Great Mystery for novice growth investors and the Prime Directive for veterans.