The journalist Tom Vanderbilt, who spent a year learning to sing, draw, surf and juggle in midlife, noticed something: as adults — and especially accomplished ones — we avoid being beginners precisely because we're so used to being competent. The gap between how good we are at our established thing and how bad we are at the new thing is painful, and we read that pain as a verdict: I don't have the knack.
It isn't a verdict. It's just the ordinary cost of entry, felt more sharply the more status you have to lose. The people who keep learning across a lifetime aren't the ones who never feel that discomfort. They're the ones who've learned to expect it and keep going anyway.