Columbia professor Rita Gunther McGrath lays out "the principles of healthy disengagement" from an underperforming business. "First, identify the warning signs. Often, these are qualitative leading indicators rather than quantitative lagging ones. Next, create a way for the import of the numbers to be recognized. Then, once the decision has been made, determine the situation you are in and design the disengagement strategy that makes the most sense."
Adapted from McGrath's book The End of Competitive Advantage: How to Keep Your Strategy Moving as Fast as Your Business.