In this quote, Brendan Behan is suggesting that it is a kind and honorable act to let go of a bad or unsuccessful joke. He is implying that holding onto a bad joke and continuing to inform it can be viewed as a negative action, as it may cause pain or inconvenience to others. By forgetting the joke, one is showing consideration and empathy towards those around them. Furthermore, Behan might also be implying that it takes humbleness and self-awareness to acknowledge when a joke is not well-received and to move on from it. In general, this quote highlights the value of bearing in mind others and picking generosity over ego.