Challenge can be an important source of self-knowledge

Challenge can be an important source of self-knowledge, since those who pay attention to how they react, both emotionally and physically, to challenge can gain useful insights into their own weaknesses.

Which one of the following most closely conforms to the principle above?

(A) A concert pianist should not have an entirely negative view of a memory lapse during a difficult performance. By understanding why the memory lapse occurred, the pianist can better prepare for future performances.
(B) A salesperson should understand that the commission earned is not the only reward of making a sale. Salespeople should also take satisfaction from the fact that successful sales reflect well on their personalities.
(C) Compassion is valuable not only for the wonderful feelings it brings, but also for the opportunities it affords to enrich the lives of other people.
(D) While some of the value of competition comes from the pleasure of winning, the primary reward of competition is competition itself.
(E) Even people who dread public speaking should accept invitations to speak before large groups. People will admire their courage and they will experience the fulfillment of having attempted something that is difficult for them.