Act the way that you want to feel.

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".

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.

Writing makes me happy.

Turns out that people who try new things, go new places, learn new skills, etc. are happier. This can be tough, because novelty and challenge also bring frustration and irritation - but if you can push through that, novelty and challenge can bring enormous happiness rewards.

The days are long, but the years are short.

A book is a better way to develop a complicated idea, or to tell a big story and to show how ideas weave in and out of each other, which is something that comes up a lot in happiness because all these ideas are interconnected.