I always found this very scary. If I'm not the largest influencer (positive/negative) then I have bigger problems to worry about.
This is not so different from the standard sales approach of gaining the confidence of an SME on the client side who advises the decision maker.
The successful relationships I've had were always ones where my partner had their own, multiple criteria for happiness. I want to be at most say, a third of someone's life and contribute as much to their emotional state.
Between work, hobbies, social circles, working out, etc etc, I've always found relationships to fit into that but they place about no. 3-4, and anecdotally, its always made for better outcomes. When they hit no. 1 or 2, it means we're both giving up on something that's a significant part of our character, and I've never found it to be a positive indicator.