The following debate among psychologists may be enlightening.
Happiness: Is it in your genes or in your head? - By Steven Pinker, Martin Seligman, and Robert Wright - Slate Magazine
I agree with Seligman on some points(famous for "Learned Helplessnesses" phenomenon), Pinker on others.
I
hope Seligman is right. But that is usually not enough to make something true.
But I figured it wouldn't hurt to borrow from their debate, considering the early agreement that "happiness" is essential to success.