One way I have kicked my obsessive thoughts about someone I felt was paying attention to me was to find out more about them. I had a teacher who was very willing to pay attention to his students. I looked up his number to find out where he lived and found his house, he was married and had kids. It went along way to realizing there was nothing special between us he was just doing his job. He was my teacher for two more years and I was able to give up my obsessions around him. I was able to see that he had similar interests in other students as well so I just read too much into it.