Live to make your partner happy.
My mom told me this when I was young. She said, "If you and your partner live every moment to make the other completely happy, all of your needs will be met and you'll have no reason to distress." Of course, my high school ears shut her off. But after multiple relationships and a divorce, I realize that she was right. I've tried her strategy in my current relationship, and I see that she knows what she is talking about. Of course, it's a two way street. My guy lives to make me happy, and I live to make him happy. It only works if both people are committed to each other.
It may seem silly or unconventionally selfless, but it makes sense. If both people strive to make the other person fulfilled and happy, then both people end up fulfilled and happy.