Courage is needed when there is a deep fear of an outcome. I believe that Atticus fears an all white jury. He states that courage is following through even when one knows he is defeated:
"I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand. It's when you know you're licked before you begin but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do."
Atticus fears the verdict. He realizes that Tom Robinson will be convicted. He realizes that prejudices are at the heart of Maycomb.
Atticus fears that his children will suffer because of his decision to defend a black man. In the face of fear, Atticus finds the courage to follow through with the trial. No doubt, Atticus had fear but he mustered up the courage to do the right thing and at least "try to win." Even though Atticus fears that he will lose the trial, he tells his children that he must try:
Simply because we were licked a hundred years before we started is no reason for us not to try to win.
No doubt, Atticus fears the past and knows the future will be difficult while he is trying to represent Tom Robinson. Atticus conquers his fears and defends Tom Robinson to the best of his ability. He does an outstanding job at proving Tom Robinson's innocence. Still, it is not enough for an all-white jury to find Tom Robinson not guilty. That is what Atticus fears. That is why he stresses the importance of courage. Courage is only needed when one fears something:
Atticus's own actions in arguing the Robinson case demonstrate this kind of courage, and his behavior throughout embodies values of dignity, integrity, determination, and tolerance.
No doubt, great courage is needed in the face of fear. Truly, Atticus would not have needed courage if he had not had fear.