Normally, successful people are highly committed to their work. Here is the problem: the more committed we are to a given path the harder it is for us to admit when it's time to leave. This is why leaders need term limits — it is often just too difficult for them to set these for themselves.
I have had the privilege of working with more than 120 CEOs. I've also had the unfortunate privilege of working with four CEOs for whom it was time to leave. I said to them, "It is time to leave now. Leave with dignity. Don't embarrass yourself." I failed in all four cases. They didn't leave, and a couple of them were on the covers of national magazines — embarrassing themselves and the company.
Why didn't they leave when it was time to go? Because it is incredibly difficult for highly successful leaders, who have put their heart and soul into something, to look into the mirror and say, "This doesn't work. It's time to go." The very fact that they are so highly committed to what they are doing makes it very hard for them to hear contrary information. This is true for leaders at all levels, not just the CEOs.