I'm currently also dealing with trying to forget someone too. I'm in a relationship with someone else and I love him very much. As much as i love him, my senses still show shimmers of spotlight on the old person i used to like but never gotten (Like as if my soul is with my Bf but my attractions and flings still linger with the other dude.). It's hard to try and cover up the fact that you used to love/like him/her. And i know, because im going through it now. But i know i'd never hurt my Boyfriend. He's waaaay too precious to use all the energy on stupid love triangle shit. (And frankly, the old thing isnt even much of a pull anymore)
To be honest i don't think you can ever really forget someone you used to love/like. And if you can, then it takes a REALLY long time and a health distraction to make it work. But hardly anyone can do that, not even myself and i try to (Its that or you become a robot or an unemotional person). Its hard it really is.
You can probably just make it not as strong by just doing different things, and getting involved with different things. That's the best i can say :<