Happens all the time dude.
Its a little known fact that all the 'record' buttons in the world have a telepathic link with anyone that knows they're being recorded that sends out one of a number of random instructions to the brain of the player. They include, but are not limited to
- Forget the riff.
- Forget what comes next
- Forget number of repetitions
- Forget variations within section
- Suck. Nao.
- Suck, as soon as you think youre nailing it
- Try to play at different tempo
- Lose sense of pitch, have to play again later. (This mainly happens when you get an otherwise good take)
- Play wrong fret
- Play wrong string
- Forget length of lead-in, forget to play at all
And many, many more. Seen em all, done most of em myself.