why is atticus concerned that jem take the lesson to heart in chapter 11?

Atticus explained to his children that Mrs. Dubose is an example of true courage. Even though she knew she was going to die, Mrs. Dubose wanted to be free of her addiction. Atticus tells Jem that courage is about more than men with guns. Instead, it is about knowing you're going to lose but sticking to your views and fighting anyway. Mrs. Dubose won, because she died beholden to nothing. Atticus calls her "the bravest woman I ever knew."

Atticus wants the children to understand that courage has to do with the fight for one's personal goals, no matter what the odds are against achieving the goal. Heroism consists of the fight itself, the struggle against fate, circumstance, or any other overpowering force. Mrs. Dubose's goal is to break free from her addiction to morphine. Her struggle against the clock and mortality is easily compared to Atticus's struggle to uphold his own morals despite the hopelessness of his case and the lack of support he has in town. According to Atticus's definition, he and Mrs. Dubose are both brave, even heroic, and he wants the children to follow their example. Even though Mrs. Dubose is a mean and bigoted old woman, she does have good qualities that demand respect. Atticus wants the children to see that though many of the townspeople are ignorant and racist, they also have personal strengths and are not fundamentally bad people.