I finished reading "Ambition", a book by the sociologist Gilbert Brim. One thing I took away from the book is that we humans seem to be most happy when we're faced with what Brim calls "manageable difficulties" -- challenges that are neither too easy (because then we become bored), nor too hard (because then we become discouraged/depressed). Brim says that humans are driven towards mastery and achievement in whatever field they set their eyes, or minds, or souls on. We are an ambitious kind, always striving to do better, not only in ordinary careers, but also when we meditate or when we walk on spiritual paths, supposedly getting away from it all. In all cases we will try to do our best to achieve mastery.
Brim cites the "25% rule", discovered by another sociologist whose name I forget. The rule states that no matter what level of income we achieve, we instantly shoot for 25% more. Brim says that he suspects this rule holds true not only when it comes to money, but also when it comes to fame, spirituality, etc. And when/if we get that 25% increase, we feel a brief moment of happiness ("brief" is the operative word here), then we roll our sleeves and keep working for that elusive moment when we'll finally have made it or achieved it.
I tend to agree with Brim. It seems to me that the best we can do is use our innate ambition to achieve something meaningful not only to us, but also to others. And maybe we should try to enjoy and prolong those too-brief periods of happiness :-) For us computer geeks, this possibly translates into working as teams on Open Source projects and enjoying the process more than the end product.
You can read some excerpts from Brim's book here.