Rough day today...i developed a working mean reversion strategy a few months ago, and recognized from the outset that, while it was a solid producer, there were/are outlier days that are devastating to such an approach. I run this as both an automated and as a discretionary system. For my automated system I eventually solved it by simply stopping for the day after a single loss. Not exactly sophisticated but it has been effective. However, the discretionary approach has been another matter. Today I recognized that this was most likely one of those days, and yet somehow I continued to trade on what i can only call 'hope'. It was not hope in the purest sense, but it was 'hope' that statistics would prevail, that the averages would prevail, and that my suspicion that this was an 'outlier' day would not prove true. Obviously, today was no day for mean reversion.