Whenever you're in a stressful situation like public speaking or being interrogated by the NSA for your 16 terabytes of hardcore tentacle porn (@Boukert), Perhaps in a job interview.
Just imagine holding each and every person down and aggressively shitting in their face until they pass out or drown. Whichever comes first.
I find this method to be incredibly useful.
In this case the less fiber in your diet the better. Also go on a fast food binge beforehand if you can.