Kurt Vonnegut speaking to John Irving while Irving was administering the Heimlich maneuver in response to Vonnegut's uncontrollable coughing..."John,stop- I am not choking. I have emphysema.
Humor is an almost physiological response to fear.
Laughter and tears are both responses to frustration and exhaustion . . . . I myself prefer to laugh, since there is less cleaning up to do afterward.