I'm currently implementing notifications in my Quit That! app and have been thinking a lot about the text presented. One idea I'm implementing is allowing users to customize some of the wording in notifications. Some people may want to hear "nice job" while others might cringe at that wording. Quit That! will let you customize your notification to be "F*&k Yeah! You've quit cigarettes for 82 days" if you want.
As Dave points out, it's important to really think about what you put in the text you present to users. What makes it hard is every user is motivated differently.
Do the words in your notifications matter? by Dave Verwer