I need good advice

So there's this guy I have feelings for, but I know it's never going to happen. He's engaged and even though they're long distance, I don't want to ruin their relationship cuz that's just selfish. I try to not think about him, but the problem is that I see him at least 4 days a week and we're pretty close friends so..... idk what to do. Do u guys have advice as to how to get over him?