>>When I buy a biotech, it's normally for a very specific reason and I will hold until certain specific events pass, whether that's an FDA decision on a drug, Phase II or III trial results, etc. If those events don't transpire the way I expect, the stock tanks, and therefore the story/outlook has changed, I have no problem selling and moving on at a loss.<<
You are leaving out one important reason to sell - even if a company is hitting all its targets, doing everything you hoped and more, racking up one success after another.
It may simply be overvalued.
Of course that's not so likely to be the situation these days ...
micro