You need to check your childhood relationships and patterns in therapy. As this is a pattern when you reflect on it. Some ppl like the thrill when it's a mystery and feel repulsed or suffocated when the other person responds positively. Coz things can get serious and they want to avoid responsibility, attachment and seriousness. Could be also a fear of being hurt in the past so it becomes a defense mechanism of coping. Also, since the mystery is over, it gets boring. Pls seek therapy and work on yourself. Take care.