How can i clear my head of him????

I dated him for a few months but really, truely believe he could have been the one for me. He doesnt know this and didnt know that i had fallen in love with him (if that is possible in such a short space of time, and so few dates). Several months on I cant stop thinking about him and what might have been. he didnt want anything serious with me at the time so I know it wasnt meant to be but why do I continualy think about him and wonder....ive got a good life, lots of mates, fab family and am always busy esp with work.... How can i eradicate him out my head and move on????