Once you’ve conquered Maslow’s original hierarchy of needs, dig into his final need that he added later in life. Achieve not for yourself but for your community or your world. Transcend the self, and feel that higher order need. As another commenter mentioned, altruistic endeavors are a good choice. Even things like being a Boy Scout leader can be hugely fulfilling of that broader need.
My wife and I went through an extremely rough patch in our marriage where we considered divorce. We got our finances in order (even after going through a bankrupticy) and went to marriage counseling with a fantastic marriage counselor.
Now more than a decade later, we are pre-marriage mentors and financial coaches through our church. It is more fulfilling that I could have possibly imagined.