"I reckon if he'd wanted us to know it, he'da told us. If he was proud of us he'da told us."
"Don't you cry, now, Scout...don't cry now, don't you worry-"
Jem realizes that Atticus would not want them going around telling people that he was the best shot in town and that they should just keep it to themselves.
Jem is sad because he wanted to find and thank the person putting the gifts in the hole and now that it's plugged, he will have a harder time meeting the person.
Jem comes to the realization that Mrs. Dubose was the real definition of someone with courage, also that courage is defined by someone who takes on a challenge even when they're in no position to overcome what they're facing. He also learns that courage is not a man with a gun in his hands who is a good shot