For starters, understand yourself, what makes you feel this person, whether it causes you suffering. Maybe it's a physical attraction or just a crush? The desire to possess or addiction? Maybe a combination of several factors. Analyze your feelings.
Consider the fact that the person you like, actually the same as everyone else, and not "white and fluffy". Look around you, because around you there are other people, maybe someone of them like you, and he is also trying to achieve a reciprocal feeling.
Stop looking for any means of contact with that person, remove him from your social media pages, erase phone number, forget his email. Don't call him and don't write. It is not necessary to impose the society, because of this you will not achieve anything. In addition, when you often see, your feelings will fade away very slowly, therefore the General friends should stop to chat. Moreover, you will constantly be tempted to ask them about it.
If you have any items reminiscent of this man, get rid of them. Regardless of whether it is soft toy or just a picture. Think about the reasons of your affection. What do you like in man? How often do you resurrect in memory the bright images that lasted only a few moments? Start living in the present. Make new friends, socialize, attend parties and clubs. As less time as possible try to spend alone alone with my thoughts.
Accept the fact that you'll never have a relationship with that person. Do not comfort themselves with the hope that he will eventually understand their mistakes, will appreciate your reverent attitude, and finally will honor you with their attention. This will never happen. Do not visit public places, where it often happens away from them.
Take care of yourself, change your hair color and hairstyle, update your wardrobe, start a pool, join a gym. Avoid fatigue and boredom, doing something or chat with friends. You will not even notice how quickly you forget the personthat you like.