When I find myself focusing overmuch on the anticipated future happiness of arriving at a certain goal, I remind myself to 'Enjoy now'. If I can enjoy the present, I don't need to count on the happiness that is (or isn't) waiting for me in the future".

I needed to change the lens through which I viewed everything familiar.

What's fun for other people may not be fun for you- and vice versa.

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.

Feelings follow actions. If I'm feeling low, I deliberately act cheery, and I find myself actually feeling happier. If I'm feeling angry at someone, I do something thoughtful for her and my feelings toward her soften. This strategy is uncannily effective.

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.

When I thought about why I was sometimes reluctant to push myself, I realized that it was because I was afraid of failure - but in order to have more success, I needed to be willing to accept more failure.