(and if so, share here)
They say that the only way to fully understand something is to teach it. I am years away (if ever) from fully understanding Japanese (I failed the N4 exam in 2025), but I tend to overthink small things, and I have had multiple cases where I shared an epiphany with my (native Japanese speaking) partner, and she said “wow, I’ve never thought about it that way.” To be fair, there are also plenty of times where she has said: no, you are wrong. 
As a side note, the same thing has happened in reverse. She often asks me something like “what is the difference between these two English words?” And I realize I can’t explain it, so I have to stop and think hard, and sometimes even consult a dictionary. Result: I learn something about English!
If others have similar stories, please share them in this thread. I can’t think of specific examples right now, except for this one because it happened very recently:
The word なくなる does not need to be memorized, because it is literally just ない (not existing, in adverbial form なく), with なる (to become) attached. Thus it means “to become not existing”. Or, to disappear.
Even better, I presume this framing explains why なくなる is translated as the polite “to pass away” (compared to 死ぬ translated as “to die”). The LLMs agree with me, but maybe we’re wrong.
)