I won't cheat. Period. But I can understand the drive, when your woman is always anxious, angry or just plain miserable no matter how hard you try. It's just who she is. I think it boils down to Daddy issues. If Daddy was an a-hole, well so are you and there is nothing you can do to change how she feels about you.
Before we got married, my wife told me she loved me almost because I was so unlike her father. I was attentive, caring, emotionally aware, easy-going yadda etc. But am no push over, I am admittedly a pretty driven, ambitious person. As the years went on, I noticed she began to accuse me of doing all the things that her father did to her mother. That she felt like a single parent, that I did not sympathize with how difficult her life was, and that I demanded her to toe the line with all my plans (daily or long term). It was off the walls absurd, because I listen to her daily, play and help out with the kids daily, do my chores around the house daily, and I am quick to accommodate her schedule. Every time I suggest we do something fun together, she feels burdened to have to plan the logistics even when I offer to do so. She complains how unfair it is that I am so happy (with my job, running, hobbies, love hanging out with the kids etc), while she struggles with her job, how the kids behave around her, and that she has no hobbies. The increasing distance is affecting our kids, I know they are concerned and I can't hide it from them.
I chat with cute girls everyday at work and notice myself getting more friendly with them than I am with my guy friends. I have to stop myself because I know they are starting to meet a need that is not met at home. Sucks, but there it is. I won't cheat. I have that fine line, but I can feel the pull. Starting couples counseling next week.