I saw something not very long ago which stated that due to constant seeking for happiness, humans are generally hard wired never to actually get it, even if they achieve the thing they believe will make them happy. It's like an inherent grass-is-greener syndrome that we can't quite shake.
It seems to take a lot of self-control of one's emotions, mentality, and resolve to truly find that they are happy - right now, right here. Almost as if the persistent illusion of a future (when it seems all there is is right NOW) is what develops an incessant thorn of anxiety which won't leave us alone, and any moment tainted by anxiety or generally any negative feelings about one's immediate situation is a moment worth being free of...something has to be better than this, right? But each and every moment is an expression of what your life can be.
The question then becomes - do I take this moment and make it be something? Or do I sit as a mere observer and let things happen to me?

Or as Robert Anton Wilson would say,

YOU are the master who makes the grass green.