Is this to make me feel guilty? If you wanna know dump them and find an even better guy.
Honestly there's no way to do that! If your heart is mad in love with someone you can't tell it to stop but u can just tell your heart that that person is one someone else now and if it loves him then just do what that person wants. That person wants to be with his love so just get that person be together with his love. Make your heart do this and I guess your heart will try to forget that person or that person would be with you! Idk its just destiny , I've seen this in movies!
I'm guessing this sounds like you broke up with someone, who now is with someone else? I've never been in a relationship or known of anyone having a crush on me, but I've had a few different crushes. I don't know if these would help for you, but they're what help for me some. But I have to say, love is strong and it can be really hard to get over it.
*fall in love with someone else, anything else : Movie character, best friend, God, adorable kids, puppies, occupation
* have a decent conversation with the person- I can't explain why, but this helps the most for me
* journal your feelings and then delete them (or hide them), sometimes it helps to get your feelings out and to talk about them with yourself on paper. Then (I like to keep anything I journal,) but you can get rid of it so you don't think about him anymore than you need to.
* don't make yourself feel unimportant or depressed, but make a list of the reasons he wouldn't like you in your mind- not on paper! This doesn't work for someone who does or did actually like you; it just helps me for my crushes. I usually just assign each of my crushes one or two reasons why he wouldn't like me.