The purpose of life is not to be happy. It is to be useful, to be honorable, to be compassionate, to have it make some difference that you have lived and lived well.
Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm. But the harm does not interest them.
I still indulge in a glass of wine or chocolate - treats are mandatory. Without deviating from the day-to-day healthy diet once in a while, it wouldn't be sustainable for me, and that's what I wanted: an approach to eating to last my entire life.