Chug an extra cup of coffee. Run an extra 20 minutes on the treadmill. Whatever it takes, don't fall asleep right now. Because the stock market is trying to lull us again.

Three weeks have now passed since the market's January 22 low. And, despite a couple of rough days last week, stocks have generally "held it together." Including today, the Standard & Poor's 500 index has ended in the plus column nine out of the past 15 trading days -- a respectable run, though hardly a barnburner.

The risk is that, after another week or two of generally rising prices, the market could roll over again in late February or early March. I'm not necessarily predicting such an outcome -- simply cautioning you to be on the lookout.

The January bottom was a pretty good one, but it lacked certain technical characteristics that have signaled every major low of the past 50 years. Normally, for example, key momentum gauges will bottom a few days to a few weeks before the indexes. This time, the bottom for price as well as for most rate-of-change indicators occurred the same day.

There's always a chance, of course, that "this time is different." More likely, though, the S&P will revisit its January low (1310) at some point, and even break through it by at least a marginal amount.

Meanwhile, I advise you to be very cautious with new purchases. Yesterday, American International Group (NYSE: AIG), the world's largest insurance company, disclosed that it had underestimated its losses in October and November from insuring mortgage-related instruments by about $4 billion.

AIG will recover from this setback, as will other businesses that fell victim to similar underestimations. I'm not saying it's going to happen tomorrow, but it will happen.

Stay tuned.