When we're playing music we're just making it up as we go along.

So maybe there is a right or wrong way, but in the moment, what you're playing IS the way. Keeping your fingers on the strings, keeping the rhythm moving along without pauses, even if it isn't the way the song goes, what you've played (or sung) is they way it went THAT TIME. Embrace the variety, appreciate what came out that time. Playing a song perfectly is not as important as playing it.