"Strong Lesson" - that suggests something more than learning - for example - "Fire is hot", "Falling hurts" or "Volunteering as the rope in a tug of war between my two bigger (5+7 years older) brothers isn't a good idea". But here's the thing, most things you learn are over a period,
this so rarely happens. Those things involve a period of introspection that likely takes more than the whole of your childhood.
But as it happens, I have an answer for you. And, we're back to books. I learned to read quite young, by the time I went to school at 5 (I'm an August baby) I was reasonably fluent, and I had progressed past the "Janet & John" primer. So, my first day at school involved learning that all the other children in class could not read the book we had been presented with. I learned that it felt quite good to be achieving. I distinctly remember bringing the book back home and triumphantly saying to my parents "I can read this!"
Their response - "We know you can, dear" - taught me the strong lesson at an early age: life will be full of disappointment.
ETA I wonder if......of course there are
facsimiles on line