"Never use the word 'always', and always avoid the word 'never'." (https://youtu.be/5NagVDLvtUo?t=311 [~5:11])
I doubt he was the origin of the aphorism but I first heard it from him. It's so much nicer to listen to and learn from people that are clearly knowledgeable in their areas of expertise, but don't try to present themselves as all-knowing and infallible.
I haven't watched nearly all of his content but I never (heh) found his speech patterns to be stilted or awkward like he would frequently warn about either.