If a woman/man has many partners before you and you enter a relationship, only to find that he/she eventually cheats/chooses not to be with you anymore, isn't that more a hint that you were not satisfying enough? both mentally and physically? I guess more to the point, they like sex and want lots of it, and they want it to be good. Liking sex doesn't mean they like having sex with anyone they can get their hands on.
I don't see the connection where it means that they suck and you did nothing wrong and your poor heart was broked. Sure, there are better and worse ways to handle things, but if you can't keep up, are you expecting them to just deal with your shortcomings?