Don't let perfect be the enemy of good.

It's true that people do assume that people who are critical are smarter than people who are uncritical.

When we don't get any treats, we feel depleted, resentful, and angry, and we feel justified in self-indulgence. We start to crave comfort - and grab that comfort wherever we can, even if it means breaking good habits.

I'm a creature of routine, and I hate feeling incompetent, so I avoided novelty and challenge. Making an effort to push myself in that way has brought me surprising boost.

Your unhappiness doesn't help anyone else - and in fact, as I mentioned in another answer, happy people are more altruistically inclined. So happiness is not a selfish goal.

Be a storehouse of happy memories.

[S]tudies show that one of the best ways to lift your mood is to engineer an easy success, such as tackling a long-delayed chore.