The Reason to Leave
My marriage was rocky from the start, rooted in what I once dreamed of as the scars in the landscape of my life due to having been molested as a child. And I don't like being alone. I'm a people person.
I spent a lot of years imagining there was someone out there for me, some Prince Charming, some True Love (TM), someone I was meant to be with, some better man for me than the one I had.
And as long as I had it in my head that I was leaving him for the opportunity to be with a better man, I stayed, hesitant to follow the pattern I had watched others follow of new face, same shit.
For most of my marriage, there was someone else I was emotionally invested in even it was never consummated. I finally asked for a divorce during a brief period when there was no one else pulling at my heart strings and filling up my mind with fantasies of a better future with a better relationship to a better man.
Die to my health issues and our special needs kids, the divorce was long and drawn out. We were in California and the law there allowed us to live together while gradually separating our lives both legally and physically.
So happenstance allowed me to repeatedly experience the following while extremely impaired and scared to death of leaving:
I would get chatted up online by some guy, go "Ew! Why am I LEAVING??? Other men are so much worse!!!!" and then get a reality check by PROMPTLY spending five whole minutes with the future ex and remembering "I'm NOT leaving him FOR someone else. I'm leaving him because I would rather be alone than with HIM anymore."
I'm hardly the only person who doesn't like being alone. Lots of people seem to want to line up their next squeeze before leaving this one.
Imagining you've found someone better is probably not a good reason to leave. You should leave because you are so done with THIS person that you would rather be alone.
You won't really know if THIS particular person is a good match for you unless you are actually involved with them in a serious relationship. Affairs tend to be two people seeing each other only at their "best" for the fun parts of the relationship, like sexy times, and the spouse is who gets to literally and figuratively deal with the dirty laundry and all the unattractive bits of their life.
People frequently claim affairs kill relationships. Studies say relationships in their death throes foster affairs.
They also say the person you have an affair with probably won't stick around long term. It's probably someone who has something in particular missing from your current relationship and not someone who is really a good match for a well rounded, serious, healthy relationship.
I know all the ways relationships go wrong. I still don't know how to make happy monogamy work.
But pro tip: Don't leave because you think you've found The One. Leave because you would rather sleep alone than with THIS person anymore.