World Champion Craig Valentine suggests when you use humor based on a personal failure you've had that you make sure to give the audience permission to laugh. After you explain the failure situation, smile a little, give a sincere laugh, or use a facial expression to let them know it's OK, you know it's funny and it's meant to be funny.
Laughing,
Tim Wilson
Professional Speech Coach
Free speaking tips at: http://speakingquicktips.blogspot.com
Twitter: @PblcSpkngLibr