Busy is an addiction

The issue, just like exercise, is that each time you build, the high becomes slightly harder to achieve. Part of your hormonal reward is based on the fact the thing you just built has never been built before. It’s novel and your brain commensurately rewards the new because it has learned after millions of years of evolution that doing so is collectively good for our species.

~ Rands from, http://randsinrepose.com/archives/busy-is-an-addiction/