How do you know when it's over?

Alyssa
I recently heard something that was along the lines of "you may know it's not right, but your heart doesn't. Until your heart knows, you won't be ready." 
It fits my situation perfectly because I feel like I've known for a while that my boyfriend and I aren't meant to be, but it kills me to think of not being with him. We're always butting heads, always getting upset over the smallest of things. And we have different views on a lot of things, some that I know will cause huge problems in the future when we try to have kids. 
It's killing me inside because I know it's not right, but I cant imagine being without him.