What makes us happy is really complicated and different for each of us. Some say, it is a part of ups and downs in our life, which could not be in our control. Sometimes, we have ups and downs coming due to our own behavior. Our ambitions lay a path ahead, success gives us happiness and failure gives us pain and motivation to be happy again.
On the other side, I think, if I can live with myself as I am, I can be happy forever. :-)