Paradox: Is Great Happiness Too Much of a Good Thing?

This demonstrates why there is no need to always be happy...

"Americans report being generally happier than people from, say, Japan or Korea, but it turns out that, partly as a result, they are less likely to feel good when positive things happen and more likely to feel bad when negative things befall them... Put another way, a hidden price of being happier on average is that you put your short-term contentment at risk, because being happy raises your expectations about being happy. When good things happen, they don't count for much because they are what you expect. When bad things happen, you temporarily feel terrible, because you've gotten used to being happy."

Is Great Happiness Too Much of a Good Thing?
by Shankar Vedantam
http://www.washingtonpost.com/wp-dyn/content/article/2007/09/30/AR2007093000632.html