Now that I have the time to respond, my replying will probably be superfluous. aelephant (explicitly) and shminux (implicitly) have already mentioned this technique. On the off chance that I am wrong or you want to know more, then you might want to check out the following texts: A Guide to the Good Life: The Ancient Art of Stoic Joy by William Braxton Irvine contains an entire chapter on how to perform Stoic meditation, A New Stoicism by Lawrence C. Becker tries to explain the efficacy of Stoic meditation (among other Stoic techniques) using principles from evolutionary psychology and neurophysiology, and A Man in Full provides a fictional account of a practicing Stoic.

I'm about to get on a plane. If I have access to zero price internet where I'm going, then I'll post some links pointing you in the right direction. Otherwise, you might have to wait a few days.