[stevofolife]

If you can't teach it, then you don't understand something perfectly. Perfect is a word par excellence. Teaching is indeed a skill but don't confuse it with presenting. A wise guy once said, "if you can’t explain something in simple terms, you don’t understand it". I'm sure OP stands by it and that itself is very admirable.

[bradjohnson]

Feynman also said: "Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize."

Ideas take time to digest and it's not accurate to say that if someone leaves a room not understanding what you've just shown them, you don't understand it yourself.

[perl4ever]

It's possible that's a distortion/misquote. I found where he said "I would simply say, ‘Listen, buddy, if I could tell you in a minute what I did, it wouldn’t be worth the Nobel Prize", which is about time, not intellectual ability.

[https://www.aip.org/history-programs/niels-bohr-library/oral...]

[tryauuum]

I guess previous posters "If you can't teach it, then you don't understand something perfectly" can be replaced with "Process of teaching someone will make you notice all the holes in your own understanding"

Or even without replacement. Teaching someone doesn't imply a successful result.