You tend to rebel against commitment, against any relationship that feels stable enough to restrict your freedom. You don't want to be held back; you're an individual! You're independent!
Right? Well, not exactly. See, there are reasons behind your insistence on independence, and behind that rebellious streak of yours. It's not just that you can't be held back; it's that you're afraid of what will happen if you are. Let's deconstruct this: What is it, exactly, that you're afraid of? Does intimacy with another person scare you because you're afraid to let them know the real you, or because you're scared that once they know the real you, they won't love you -- or they'll leave you and break your heart? The answer is probably a bit of both, but weighted more toward the latter. Deep down, you're afraid of having your heart broken, so you don't let anyone get close enough to do that to you -- and in the process, you probably leave a trail of broken hearts in your wake, or at least hurt feelings. So what are you going to do about it? It's time to analyze your feelings and start tearing down those walls enough to let in someone special.