[AaronBrown]

I agree with KurtSF that if you lose you should worry more about your expected win rate than your risk of ruin. After all, if your original ROR was 1%, only 4% of the time should you ever see it balloon to 25%. Therefore, even a confident player should take a hard look at her game.

I don't buy the Kelly logic in this situation for several reasons. One is that, as BillC says, it defines bankroll as everything you could get over your life, not just your cash in hand today. Second, as alThor says, it assumes you don't change your variance as a percentage of bankroll. Finally, it assumes everything is scalable, that you can bet as little or much as you like without cost.

In poker, you can't easily adjust your stake. Moving down in limit may not improve your ratio of win rate to standard deviation, and it may have costs to your reputation, or giving up accumulated knowledge about players. Playing more hands may mean playing more poker than you want, and your level of play might suffer. Turning down close bets hurts your win rate.

I personally think 25% ROR is a reasonable level to reassess, but reasonable people can differ. It will depend on your circumstances and personality. The point is to escape constant adjustment, to concentrate on poker and not on bankroll.