I was very impressed when I read The Most Important Thing™ by D’Arcy Norman. I was impressed with his candor and with his top priority – being a good father (it matches my own). I was also impressed at how well he expressed a thought that I have had before but never attempted to put into words. That thought is not the question, but the process of evaluating the components of your life and your life as a whole to ensure that they way you are living does conform to the things that you believe.
I think that anytime a person lives in harmony with their core beliefs and what they think is most important they are virtually assured of happiness. Not that they will not face challenges, but that they will feel real joy, the kind that can come even while things are challenging or disappointing. I know that I have never been unhappy as a result of something I have done when that something is consistent with my priorities. Disappointment and dissatisfaction only come when I am acting in a way that contradicts my real priorities.