How to get over him... again?

Okay so there's this guy that I used to really really like, but I thought i had moved on... now I'm seeing him a lot again and I think I"m falling for him again! How can I stop? He will never like me back (I know this for a fact... I'm not just being melodramatic), and this is just going to lead to me getting heartbroken again!! Plz help!