The third activity for sustainable happiness you experience if you manage not to worry or compare yourself to others.

To worry is thinking too much, fantasizing the wrong way. It isn't helpful. You can learn how to stop this. See also my blog about this on 23-1-2014. Social comparison is when you compare yourself or your situation to others. And then usually with someone who seems to do better. This makes you unhappy. Also about this, I have previously written a blog (on 13-3-2013). Have faith, live in the moment and compare yourself only with yourself. For example, how you were first and what you have already learned by now. Good luck!