As the great Michael Franti once said, "it's never to late to start the day over." Sometimes it feels easier to simply chalk up a day, week, year, etc. as a loss, or keep doing the same thing even though we know it's not working. In doing that we run the risk of either a) throwing in the towel progressively earlier and earlier whenever we're faced with a tough situation, or b) never having the courage to make big changes.
This can be applied to business decisions too. Especially as companies get larger, the idea of making big changes when a particular line of business or business model isn't working, becomes harder and harder. Rather than approaching situations with the mindset of "we've come too far" or "it's too late," try instead to think in terms of "it's never too late" and "what if I did do this?"
This way of thinking will free you to think critically about any/all aspects of your personal or professional life and make those big, scary changes no matter how far you've gone down the wrong path.