I was obsessed with a guy for about 5 years. That's a loooong bloody time. I was in lust. And I thought he was the best thing in the world.
One day I woke up. I had told him so many times about how I felt. He never responded. And I was glad.
But, the point is, it was hard for me to stop liking this guy. Not because he was brilliant and amazing, but simply because I had liked him for so long that it had become a sort of habit, and I just couldn't shake it.
Then, I realised I had to stop. So what I did was stay away from him. There were so many temptations to talk to him and go near him, but I forced myself not to. It was hard, and I realised that in the past that I had talked to him a lot since I started avoiding him. After a while, I started to forget about him. That, for me, was enough. It was clearly a stupid crush if it dissolved when I wasn't around him.
After a while, I stopped liking him. It took me several months, just to stop. But it worked.
And now, I am so happy for it. It's something that I'm proud of, as well. It's like I conquered him.
It might be more difficult for you, but if I can get over this boy I was obsessed with for 5 years, I'm sure you can.
Good luck.
And remember, there are probably so many more guys out in the world that are worth your attention. Forget about one who doesn't return your feelings!