If a stock is not following through post-breakout despite continued good behavior in the averages and other leading stocks, that would be one reason to close a position before price drops to hit the stop loss. Another reason would be if the desired amount of volume does not enter the stock in the first few days following entry. In essence, if the stock is not doing what you expected it to, the stock should be sold.
There is a fine line between being patient and allowing a stock to find its footing post-breakout and selling the position in order to invest the money in another promising actor. You might wish to review charts of past big market winners to see how much stalling action there was immediately after breakout, but before it began rising in earnest.