I know myself "in a relationship" as a man who is satisfied and settled. I am no longer driven by the energetic part of the sex-brain that is hunting for attractive and available women. When I have a relationship to lean into I can settle down into my life's work that is about more important things.
And I can still recall twice in my life, the thrill of that moment when I realized my heart was spinning out of control and there was nothing I'd rather do than be with this other beautiful person. Whew! Only twice? Dang, that's inspiration enough.