A sense of humor helps. When I simply can't take it anymore, I abuse guild/party chat like a little bitch. You can try whining to others about your sucking skillz, or you can relate some maple mesos LOL anecdote - I don't know.
Either way, try to do something that will entertain your audience, so you won't get expelled. Good examples of how not to entertain an audience are dotted everywhere throughout this guide.
If you're high level, consider heading over to lower level areas to help other people out for a while. Unlike some of the other points outlined here, this is actually a kind thing to do - especially in the mines near the pub, where revives and speed aren't expected.
Over time, you may find that your temper will get shorter and shorter. Use this to your advantage by encasing yourself within a black shell of cynicism, punctuated only by self-depreciating insults.
Congratulations, I can't believe you actually read this far. Now that I've listed every single tip that I know to the world, I fully expect someone to copy/paste this week later and get full credit for it.