It's so sad when someone gets involved with a person that's beyond perfect for them, and they can't seem to realize how great they are. Instead of cherishing what the two of them have, the individual decides to go looking outside of their "situation" for some...FUN. Yup!...fun.
Don't waste anyone's time when you aren't truly satisfied. If you need someone else to satisfy your needs why your loved one is not present for whatever matter, then maybe it is time to move on. I'm no figure of authority or an expert on relationships by any means. It just sucks to watch something good go to shit because of greed.