For of all sad words of tongue or pen,
The saddest are these: “It might have been!"
All too true. The stuff I really regret – thankfully, there’s very little of that — is what I didn’t do.
Thanks to the ambiguity introduced by the word “just”, the author of the message might be expressing regret that the act had escalated beyond kissing and into serious “viewer discretion is advised” territory, which is probably something you shouldn’t be doing in a friend’s kitchen.