"The conclusion is clear: it is smart to be happy"

As a generally happy person, I was happy to read this: Are Happy People Dumb? by Shawn Anchor.

The real story of happiness is that every person has a range of potential — in terms of intelligence, athletic ability, musicality, creativity, and productivity — and we are more likely to achieve the upper bounds of our brain's potential when we're feeling positive, rather than negative or neutral. ...

In fact, happiness is the single greatest competitive advantage in the modern economy. Only 25% of your job successes are predicted based upon intelligence and technical skills, though we spend most of our education and most companies hire based upon this category. The "silent 75%" of long-term job success is based upon your ability to positively adapt to the world: optimism, social support creation, and viewing stress as a challenge instead of as a threat.

As the song goes ... Don't worry. Be Happy.