OP didn't cheat, he did what you're suppose to do. If you are falling for someone else, you break it off with who you're currently with before ACTING upon that interest. He probably became good friends with the other person and realized he felt more. So to make it so he wouldn't cheat, he broke it off with his current GF. He did everything absolutely correctly, although lost both in the end. People need to realize, the new dating feeling butterflies disappears after a while, and if that's what you search for instead of realizing its normal to not have them forever, you get yourself in a loop of thinking you're missing something when you're really not. There's so many stages of a relationship! Being with my husband for 14 years, married for almost 11 of them, butterflies stopped after a year or two. Now we're just best of friends, in love and enjoy our mutual company! Things happen when they're meant to happen. Enjoy it!!

Why cheating? You can develop feelings for someone that you're not together with, you know?