The major reasons to sell a stock are:

• If the basic business changes and you are unable to understand it very well.

• When the business changes and the management is not capable of handling the business.

• When the overall economic condition of the country gets bad enough to decrease corporate earnings growth of the company.

• If you bought a mutual fund because of the record of the manager and that manager leaves the fund.

• Finally, if a stock becomes overvalued enough that the shares have a substantial risk of declining price in future.