Health isn't a choice, though, although there are things I can choose to do to maintain it. But choosing to be joyful feels to me like choosing to eat something that isn't in the cupboard: it might sound good, but it isn't going to get me very far.
Almost 2013! Start on January 1st with an empty jar. Throughout the year write the good things that happened to you on little pieces of paper. On December 31st, open the jar and read all the amazing things that happened to you that year.