Editor's note: As a special bonus to TheStreet.com readers, we will be running an updated version of Jim Cramer's "Twenty-Five Rules of Investing," from his latest book, Real Money: Sane Investing in an Insane World. Here's Rule 16.

Professionals and amateurs alike hate selling their dogs. They keep hoping, keep assuming, that a sinking stock is wrong in its direction. They rationalize that the weakness or lack of interest they see is and will be fleeting, and that people soon will recognize the value that the holder sees in the stock.

That's all well and good, until you need money.

Most fund managers have fabulous marketing teams that are able to hype their funds regardless of performance. Despite that and despite the shameless way this industry supports just about anyone who runs money if the money-runner is willing to kick back to the sources of funds, managers do get cash calls. They periodically have to redeem shares they own for cash to send back to unlucky investors.

When they do, that tendency to keep the dogs develops a sinister side: Good stocks get sold to subsidize the losers. You then get a self-fulfilling spiral as the bad stocks stay bad. They usually keep going down. And the fund, without the good stocks, keeps sinking. They never learn my rule:

Never subsidize losers with winners.

Individuals do the same thing. They have only a finite amount of capital to invest. Rather than take the medicine -- the loss -- they hold on to the losers and sell their winners.

My advice to anyone who is stuck in this position is quite simple: Sell the losers and wait a day. If you really want them, go buy them back the next day. I also am certain that you never will.

At the time of publication, Cramer held no positions in stocks mentioned. Jim Cramer is a director and co-founder of TheStreet.com. He contributes daily market commentary for TheStreet.com's sites and serves as an adviser to the company's CEO. Outside contributing columnists for TheStreet.com and RealMoney.com, including Cramer, may, from time to time, write about stocks in which they have a position. In such cases, appropriate disclosure is made. To see his personal portfolio and find out what trades Cramer will make before he makes them, sign up for

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