Tough to do? Back off on the leverage and exercise stop discipline. The TRADER is in control of his "single large losses"... (not that we can't have a string of smaller ones which add up to something significant...). If you take a big hit on one trade... it's your fault alone 99% of the time (allowing for external shock like 9/11).
Strangely enough, the 9/11 happened during a clear downtrend, so it wouldn't have caused further losses for those trading along the main trend. Of course trend faders, and bottom pickers got burned.