Oddly enough, they are almost one and the same. Age, I believe, has nothing to do with it. It's all about what is inside of us, and for each of us, that's different.
We are, in one school of thought, "good enough" the day we are born. Any day we ask ourselves that question, we are "good enough". It's just a matter of accepting that fact, and you're there.
I have met and heard of children who were already there, while I have met senior citizens who still aren't there. We can all be there, the moment we accept that we are just who we are and that we are good enough right then, at that moment.
And no, I'm not there yet. =D