I had the same thought. Back when I was in school, I would often eat a lot of junk food after studying. It wasn't that I was tired from exerting self-control, b

I had the same thought. Back when I was in school, I would often eat a lot of junk food after studying. It wasn't that I was tired from exerting self-control, but rather that I thought I deserved it. Many other studies about morality have shown a similar effect; people who do something "good" early on are less likely to later on because they feel they've reached their internal "doing good stuff" quota. For instance, people who do programs like Teach for America have much lower rates of volunteerism afterwards than others.