How do you know?

How do you know when you meet someone that they might be the next potential "One"? I have numerous trust issues, no great shock. I have a friend in my life who has been there through thick and thin and seen me at my worst. Trust me, my worst is pretty damn bad. He is still standing as my friend. He is the first thing I think of when I go to bed and the first thing on my mind when I wake up. Sick, I know. Have you ever had someone who touched you and knew your body like it was theirs? I have and it scared the shit out of me. I have done everything humanly possibly to make this man go away and he won't. He is there, constantly. Patiently. He never ceases to amaze. I am scared to death...