Speaking from some recent experience, I'd like to address the question: Is the grass really greener? Or is it just a psychological trick that makes a 39yo man want to cheat on his significant other with a younger horniner woman in her late twenties?

fucking-GODDAMNIT.

If you don't want to cheat, then DON'T FUCKING CHEAT THAT FIRST TIME. Once you've been there, balls-deep in some 28 year old nympho graduate student who says she wants to introduce you to her girfriend, you're pretty much fucked. SERIOUSLY.