So, I am dating this guy, but I also have a crush on this girl (we do flirt a bit, but it’s just casual, nothing too bad)… I want to date the girl as well, but I know that my boyfriend doesn’t like polyamory, so how should I try to stop feeling romantic attraction towards her? I’m trying to stop flirting with her as well…. any other ideas?

This is pretty impossible, unfortunately. It’s hard to just will yourself out of feeling something - if we could just turn feelings on and off when it suited us, it would be so much easier to be a person.

When I find myself with a crush on someone I really do not want to have a crush on, I just try to avoid them. I don’t go out of my way to talk to them, be around them, impress them, etc. Taking some distance and not indulging the crush helps, but it certainly doesn’t mute the crush entirely.

But that assumes you don’t want to continue being friends with this girl. If you want to keep hanging around her, see if you can convince your mind to transmute the crush into a non-romantic affection. You can be really close with someone, spend lots of quality time together, be there for each other, etc. - all the things people do in relationships - without physical/sexual intimacy. 

Ultimately, though, there’s no “one weird trick” to just stop feeling romantic attraction toward someone. If there was, history would probably have turned out a lot differently…