[silentbicycle]

Buddhism is primarily about reducing the amount of suffering in the world, in both ourselves and others. Part of this includes trying to let go of the cycle in which you think you need _ to be happy, strive to get it (perhaps successfully, perhaps not), then forget about it and reflexively start worrying about the next _ . This sort of behavior ("retail therapy" and subsequent credit card debt, for example) usually causes problems which get in the way of great achievements, or even being able to think clearly enough to enjoy our day-to-day lives.

(This is a quick attempt to summarize the idea usually translated as "desire is the root of all suffering.")

One can do great things because they seem like the best thing to do with one's time, not just because they're terrified by the feeling that they'll never be happy / have a meaningful life without it.