In the first place, IC, your two situations were/are not the same. You did something in the heat of the moment, presumably with no premeditation. LFL wanted to see this guy and see if she felt the same, to see if any of the feeling she has been remembering and fantasizing about was still there. She wanted to go and confirm that it was or that all there was was a fantasy of the past.
Nothing like your sitch.
All that notwithstanding, IC, telling her NOT to go is pointless. She will do what she wants. She doesn't need my permission... but if she HAS my permission, she may think twice. Telling a grown person they can't do something-- what's the point?
If you had called me that fateful night and said, "Lil, I'm here at the sports bar and just got this proposition and I really really want to do this, do you think I should?" and I started tugging on the rope and said, "Oh my God, IC, you're nuts! Do you want to throw away your marriage in one night?!? Have you lost your mind. Leave there right now!" would that have deterred you?
What if I dropped the rope and said, "You're a grown man, IC. If that's what you want to do, I won't stop you. And I'll still be your friend" and left you TOTALLY ALONE WITH YOUR DECISION.
I'm not the morality police of anyone except myself. If someone feels they need to do something, short of murder or animal/child abuse, who am I to tell them not to?
There's a saying in AA, "Don't do anyone else's inventory."