Since September is historically a lackluster month in the stock market, it can make sense to follow this modern proverb.
There is an old saying on Wall Street, which stipulates that you should sell your positions on Rosh Hashanah (the Jewish New Year, which comes usually in September or October), and establish a new position on Yom Kippur (Jewish Day of Atonement), which usually comes a week later.
Jewish investors traditionally used this method to take a break from earthly concerns, and start fresh. Statistics suggest that this method would have worked most of the time historically, partially because there are often declines in the market during this early Fall time of year.
Whether it will work in the next year, or always, is another thing entirely.
Should I sell my house without a real estate broker?
When Should I Sell My IPO Shares?