When a guy cheats on you once, he will do it again. If he gives you butterflies, remember that when he was your boyfriend, he was kissing somebody else. The sooner you set the bar for what is acceptable, the better off you'll be. We've all fallen for someone who's not great for us, but when the alarm bell starts ringing, you have to listen.
At some point you will realize that you have done too much for someone, that the only next possible step to do is to stop. Leave them alone. Walk away. It's not like you're giving up, and it's not like you shouldn't try. It's just that you have to draw the line of determination from desperation. What is truly yours will eventually be yours, and what is not, no matter how hard you try, will never be.
To let go isn't to forget, not think about, or ignore. It doesn't have any feelings of anger, jealousy, or regret. Letting go isn't winning or losing. It's not about pride. It's not about obsessing or dwelling on the past. It isn't about loss and it's not defeat. To let go is to cherish memories, overcome them and move on. Letting go is accepting. Letting go is having the courage to accept change. Letting go is growing up.
I don't think that you understand, like really comprehend this. I'm not over exaggerating, I'm not saying it just to say it, and I sure as hell am not lying. There isn't anyone else who has a chance right now because all I want is you. But I guess when I really think about it always comes down to me and you. You have my whole heart, for better or for worse you are the one I have feelings for. And no other person could even measure up.