The thing that has cost me the most money in markets has not been buying losers - it’s invariably been in selling my winners far too early. A lot of this comes down to position sizing - when you’re allocated a lot to a single name, seeing the huge unrealized gains build up is tempting. On smaller allocations, you don’t care as much, so you wait, and can make more of a calculated decision on when to take profit.
This post is sitters vs quitters - how to know if a name is cyclically cheap or a value trap, and how to hold the big winners until the fundamentals are no longer attractive.