The statement in the title is true even for those that are commonly recognized as great, as they say “here today gone tomorrow”. If you really want to be great you should not shout it out loud at every opportunity, you should recognize what your strengths are, play to them and always, always be on the look out for what you can learn to do better.
Follow the example of Toyota: get back to basics, visit the Gemba and be faithful to the only thing that can help you succeed: Learning.
The Demise of modern management
Modern managers think they are good and infallible because, after all, they were promoted or head-hunted to manage. Well, reality is a bit more complex than that. Managers can only do their job properly if they visit the Gemba often. You need to understand deeply the problems at hand before you can make good decisions. And this is true for all levels of management, but especially for the highest levels.
Modern managers, especially top-of-the-pyramid ones need to be more “workers” and less managers (which nowadays translates to bean-counters with fat wallets).