Well, it could be classic fear of intimacy, or a near cousin to it, emotional perfectionism… 
…there a lot of people, I’d guess the majority of people, who have strong irrational beliefs about what a relationship should (as in: has to, or freak out and run for the hills) look like… as if there is some kind of detailed mental checklist of each stage, what kinds of rituals, how the rituals are performed, what magical words must be said in what way at what moment, how one must fit into the family system… you must be superior to dad, or dad must be superior to you, or you must worship me, or I must worship you, or we must worship each other but God forbid we show any imperfection, weakness, need or incomplete development… some, Eric Berne and others, have referred to these deeply entrenched patterns as “life scripts”… and once you’re on board, there is a strong unconscious expectation for you to live up, or live down to, the stage directions of the life script… when people get very interesting, original, and highly self determined is when they 1, recognize that they aren’t living a life so much as their life scripts are living them, and 2, say to hell with it and begin to design their own life patterns… sometimes referred to as blowing it off and getting real…:o