Become someone your old definition of possible would have called unrealistic.

Your sense of what is possible was set by a version of you with less experience, and it has probably not been revised since. That older definition is not malicious, it is just working from an outdated picture of your resources. Becoming something it would have dismissed is not arrogance, it is the ordinary consequence of growing at all, and it happens to almost everyone who keeps going long enough.

Write down what you would have thought unrealistic for yourself five years ago and check what happened to those items. Then set the next goal slightly outside what feels credible today. The pattern is usually more encouraging than you expect.