Why would a man reject ?

I was really infatuated with a man I met. We were both single and we are both very attractive. There was only one problem, when I initiated , no strings, he completely rejected me. He told me if we ever were to make love, it would be "spontaneous". I think this is just a weak excuse but it still blew my confidence afterwards. Now I have a hard time even saying hi to him. Can someone explain this to me?