Year 2000 tech burst already proved simply long holding may not benefit your portfolio, long holding need involvement of your homework, monitoring and risk controlling.

You make money until you sell your positions, you must have your exit strategy, I classify my strategy as trend following instead of active trader. There is couple of beliefs in the Street, and see how you understand them -- "bulls and bears make money, but pigs get slaughtered", "the trend is your friend", "you can time the market", etc.