Quote 10
I am selfish. I am brave. (5.61)
This is yet another time when Tris is making "I am" statements. But here she helps us to see how bravery (and fear) isn't disconnected from other feelings qualities: Tris feels selfish because she's skipping out on her parents to join the brave Dauntless. (Of course, we'll see whether or not selfishness and bravery are always associated.)
Quote 11
"You're not a coward just because you don't want to hurt people," I say, because I know it's the right thing to say, even if I'm not sure I mean it.
For a moment we are both still, looking at each other. Maybe I do mean it. If he is a coward, it isn't because he doesn't enjoy pain. It is because he refuses to act. (10.77-8)
Although the Dauntless are all about "being brave," there's some uncertainty about what it actually means to be brave. All their training is about hurting people and Al wants to protect people, so … is he a coward? Notice that Tris is super uncertain about this issue, except for one part: brave people do stuff. Which is why she's pretty active.
Quote 12
"You're afraid of heights," I say. "How do you survive in the Dauntless compound?" "I ignore my fear," he says. "When I make decisions, I pretend it doesn't exist." I stare at him for a second. I can't help it. To me there's a difference between not being afraid and acting in spite of fear, as he does. (12.122-4)
We've already seen one way to deal with fear, with Tori's explanation of her tattoo (spoiler alert: it's a symbol); and here's Four offering us another way to deal with a fear, which is to act like it doesn't bother you (and bring a change of pants). It's an important aspect of Four's character: he's not fearless, he's just fear-resistant.