Ziyad

"if it goes wrong and you can carry on, do so"

I'd say that's the #1.

One time I saw a 'when harry met sally', where in the middle of the scene the actor farted. It was a faint fart, where you're not sure whether you heard it right. The actor, who wasn't very experienced, says: "Sorry." What he meant was: Sorry for messing up this scene. When I looked at the monitor he was terrified. The actress, however, followed that rule and continued with her next line: "oh, I forgot, you're a man." Which had everybody furiously trying not to laugh. Even the director, who was also an experienced actor could just barely contain his laughing.

When we watched the scene back, thanks to her reaction his "sorry" meant "sorry for farting in front of you in a restaurant".

I liked this version better than the real when harry met sally scene.