I wrote an iPhone app for rare book collectors called Titlz. http://davidlains.com/titlz The market for this kind of app is tiny but I still had fun building it and learned a lot. It has made about $20 in two months.
Many people have a hard time realizing they are happy. It is all too easy, especially for hacker types, to continuously focus on 'the problems' or things that can be improved or tweaked. Its hard to know you are happy if you never stop and smell the roses.