I read an article the other day about how happiness is derived from this equation: reality minus expectation. When your expectations are very high and you fail to meet that in reality, you're left with a negative balance in the happy tank. This is, in a really superficial way, like going shopping at Anthropologie. My expectation is usually around the "maybe I'll find a top for $20" area and the $140 top reality leaves me with a giant deficit. This applies to all areas of life - jobs, your relationships, how quickly you're growing up, your physical appearance, your closet, your body... I could go on. If you're not sitting around dreaming up the fantastic, amazing world that you want to have and you're just going out there and doing what you love and trying to excel at it, your reality doesn't have to battle a fantastical world of expectation.
The article was in reference to why Generation Y (1970s-early 1990s births) are chronically unhappy, but I think it can easily relate to my generation (tail end of Gen Y and beginning of the trophy generation). We were raised to feel absolutely special, went to colleges that taught us to pursue that which made us happy and elevated the world (thanks liberal arts!), and yet all want to achieve a level of nice-car-and-a-house wealth... but that's increasingly hard in a troubling economy, a world of increasing college debt and lower starting salaries for college grads, and it's not that easy to make enough money for your fleet of Audis when you're doing what you love (think art, poetry, non-profits, etc.).
I struggle with expectation versus reality problems every day and I think that's a key piece in improving my daily mood! I'm trying to figure out how to slow down those wants and yet keep my long-term goals in mind.