I guess the trick is to get off a particular bandwagon while the getting's good. The true believers aren't cynical or experienced enough to make this move- they think the party will go on forever. It's the ruthless, experienced operators who make sure to sell the investment flavor-of-the-decade at the right time and walk away with a fat nest egg that they use to make even more money in the next boom cycle.
The most successful guys I know on wall street are those who hold no beliefs when it comes to investments. they have no emotional attachment to any particular stock or industry. it’s a boring way to make money, but they seem to make a lot of it.