Confession: I emotionally cheated on my ex. My ex treated me like dirt for years, at one point I meet someone else who was in the same situation with their partner. We start to chat about how awful our partners are etc and suddenly I find that I have no desire to even be in the same room as my ex, this new woman says she understands me and that I deserve better. My ex starts to get suspicious and jealous (rightly so but it didn't feel like it at the time). The other woman wants things to progress with us, I tell her I will break up with my partner but need time, she doesn't give it, eventually she kisses me on the lips one night (not reciprocated). I feel so guilty I break up with my partner, then find out the other woman just wanted to get me into bed anyway and didn't really understand me or care about me, I cut contact with her but the damage was done.
The one thing I always had was my integrity, I might not be the best looking, most confident or most successful guy but when I started to date someone I could say with pride that I have never cheated on anyone in my life. I Googled it and apparently I committed emotional infidelity so now I can never truthfully say that to a woman (and I can't really lie, it is just not a skill I have or want to have).
That isn't my reason to CTB by the way, just one thing that has been bugging me and I can't/don't want to tell anyone else about it.