The basic idea of this quote )and the lines that come before it) is that one must live life to the fullest extent possible. Thoreau is giving this as his reason for coming out into the woods. He doesn't want to be in the position where, when he's about to die, he realizes that he never really lived.
Mrs. Luella Bates Washington Jones feels sorry for Roger because she sees him out alone late at night with his face dirty. She understands that he is not a hardened criminal. He is just a kid who made a bad choice and has no role models.
Mrs. Jones decides to be a role model for Roger. When he asks her if she is going to turn him in, she says she won’t and tells him to wash his face. She seems to feel sorry for him and want to offer him guidance.
