Happiness is:
1) satisfaction about the past
2) enthusiasm in the present
3) optimism for the future

All three are partially controlled by the actual content of events and partially controlled by your own perspective.

For example, in the case of satisfaction about the past, if you are in jail for child abuse, I don't think you could get over it mentally and be satisfied with yourself. Or if you are not in loving relationships or have no family by the time you are forty then it is hard to be optimistic and enthusiastic.

With regard to enthusiasm in the present, part of it is finding work to do that you are passionate about. Another part, though, is actively enthusing yourself about things.

Studies in cognitive therapy show that we can pump ourselves up about things. In other words, content <-> emotion <-> thought is a multi-directional freeway. Hardships can upset you and cause terrible thoughts. Emotions can cause you to mess up your life and create bad thoughts. And thoughts can ruin your emotions and distract your productivity. Everything affects everything in both directions.

The important lesson I learned is that happiness is half-perspective and half-good works. If you engage in commerce with the world you will have a much better chance at being happy. If on top of that, you are grateful for what you receive, you will be even happier. Same thing with relationships. A good partner will up your happiness a notch, but your active enthusiasm and emotional investment into the relationship will make you even happier.

These ideas are instructed from Seligman's Authentic Happiness. Check it out for an even overview of happiness. Note, I left out "pleasure in the present," an important piece of happiness. However, I doubt the people reading this have trouble with indulgence.