The first off the top of my head? Shorter and more to the point. "Gabe as much as I have enjoyed the sex, I also know that I am not interested in a sexual relationship without an emotional connection/monogamy/(whatever it is you would want from ANY guy in order to have a sexual relationship)...so I am not going to be able to continue with our little rendevous anymore"
Ok total rough cut but it is a starting place! Why make it about him? I mean I know it is about him to an extent bc of old memories and emotions. But didn't you say regardless of the guy, you know it is not right for YOU, to have a sexual relationship without the emotional connection/commitment? Sorry if I put words in your mouth.
If you do feel sorry about it, you could always say, "And I apologize for using you for my own sexual pleasure, that won't happen again"
