Timmy, my eight year old son, was going to feed the fish and couldn't get the cover off the can. So he turned it sideways to get better leverage, and pulling hard, succeeded in getting the cover off. The can, being sideways, dumped its flakey contents on the counter.
I happened to be standing right next to him watching this whole thing unfold. I looked at him, and he looked at me, and I was trying to figure out the words to say. Something to the effect of, "If you take the lid off a can when it's upside down..."
As we stood there silently looking first at each other, then the fish food all over the counter, then back at each other again, he must have read my mind because he said, "Well, I learned a lesson today."