I forget whether it was Camus or Sartre that said not only is suicide repugnantly selfish, but it is an abandonment of duty to your existence. People sometimes rationalize inefficiently on this level. Rather than wallowing in self-misery, turn that negative energy into something that others can value. For example, Sartre was a POW in a Nazi prisoner camp and instead of descending into the depths of melancholy with those around him, he wrote and produce plays for others to perform, inevitably raising their morale.
Sure, existence is inane, hopeless, pointless et al., but you must do something with it. I suppose that's the pithy, shortened version of the quote.
I believe Camus talks about suicide extensively in The Myth of Sisyphus. You might try looking around for it.