Stocks tumbled today, supposedly because of a weak report on pending home sales. But that's just an excuse.

Truth be told, the market was overbought after last week's (and yesterday's) gains. If the home-sales report hadn't come out, investors would have found some other "reason" to cash in part of their recent winnings.

What do I mean by overbought? The market, like most systems in nature, has limits to how far it can go up or down within a specific time frame. You can estimate these limits, and measure the market's progress toward them, with tools such as the percentage of NYSE stocks rising or falling daily, or the rate of change in a market index, or the number of stocks touching new highs or lows.

By the close of yesterday's trading, the market's cup was about as full as it gets, on a short-term basis. So today's drop is no surprise, and nothing to fret about.

Rather, we should be watching carefully during the next few sessions to see how close the major stock indexes (and our technical indicators, based on market behavior) come to their August lows.

Worst case, at least as far I can now envision it, would be a dragging, indecisive market that failed to break out in either direction until October. Even then, however, I expect the final resolution to be on the upside as the Federal Reserve cuts interest rates two or three times, keeping the broad economic expansion intact.