How can u move on?>?

How can u move on and get ur mind of a person and even if u see them in school everday because i want to get my mind of this boy that i like so much and he doesnt feel the same way back and i told him how i feel but now he haves a gf and everything i do reminds me of him and i dont know how 2 get my mind off its hard to not think about him?????