Not many people have a job which involves others telling you out loud how rubbish you are at it - but then, not many people are comedians.
Check out this video from ComComedy, in which comics tell of the harshest heckles they've ever received.
14 Unbelievably Harsh Heckles: Comedians Reveal Their Worst Put-Downs (VIDEO)
14 Unbelievably Harsh Heckles