Lean Implementation (Why Lean Fails and how to Prevent Failure)

A friend of mine asked a great question in response to one of my recent Lean books. His question was in essence how do you keep Lean initiatives moving ahead and not going the way of another flavour of the month program. We have all seen managers with the best intentions launch new initiatives that were supposed to be the wave of the future only to see them fizzle out after a few weeks or months. Lean initiatives are no different. Many organizations have tried Lean and either abandon it completely or don't take it very far. So what makes the difference between companies that tried Lean and those that are leading the pack?
A successful launch of Lean is in some respects like getting lean with one's weight. There are no quick fixes. There are no easy solutions and it takes work. You cannot make a New Year's resolution to lose weight then go back to your old habits after a few weeks or months and expect to stay Lean. It takes discipline over the long haul.