> You are never going to get to 100% comprehension. 80/90% depending on the situation.

Key insight, people should set the realistic goal of being at most as good as their native language.

I can confidently say, in my native language, there are many times throughout daily life where I have way less than 80/90% comprehension. The other key insight though is that I can remove that ambiguity with follow up questions and elaboration if I want.

And that's what people should strive for when learning a second language. Once you get to the point where you can learn in and with the language, then you're golden. That requires far far less effort than most people estimate.