Emotional vs. Physical

There are a lot of relationships where one or both parties are cheating. What people fail to realize is that physically cheating is not the only form of cheating, but emotionally as well. Both are horrible but in my eyes I believe that emotional cheating is worse.
Physically cheating is when one goes outside the relationship and has sex or any other physical act that is displeasing to the other partner. I don't understand why people cheat anyways. If you're unhappy then break it off.
Then there's emotionally cheating. Emotionally cheating is when you emotionally give yourself to someone outside of your relationship. Forming a deep relationship with one that isn't your boyfriend or girlfriend. I believe this is worse than physically cheating because normal relationships are built on emotional foundation. The feeling that love or deep like is apparent. Though there are those relationships that are built on sex. Those don't last because there isn't any connection emotionally and mentally.
I always questioned why people cheated instead of breaking things off. It leads to heartbreak and low self esteem. I say low self esteem because he or she may start to feel as though they can't measure up to anything all due to the fact that they were cheated on. Besides, cheating is a sin. You sinned because you couldn't control your hormones or you didn't have the balls to end one relationship to start another? Nice.