One valuable lesson I learned on Wall Street is that the decision to hold a stock is identical to the decision to buy a stock. Either way, when you wake up the next morning you are long that position.
If a stock is really considered a hold or a neutral, then clearly it should be a sell. If the stock isn't expected to appreciate (or if it's not a clear buy stock), then why allocate funds to it? Investors are better served selling this type of stock, doing their homework and finding a stock that will appreciate. Holding a stock that has no identifiable upside is inherently dangerous because all stocks have downside risk, which is presumably only tolerated because of its upside potential.
Another lesson I learned is that although stock prices are unpredictable, stock fundamentals and company performance are often very predictable. Companies that have consistently generated strong profits in the past tend to keep doing so, while companies that have consistently lost money tend to keep doing so.