The doctor's remark about "facing things" is significant because, in the story, it has to do with so much more than just the fact that Finny will no longer be able to play sports. Not only will Finny not be able to do the things at which he had always naturally been the best - sports - but he will also have to come to terms with the realizations that his best friend might have hurt him on purpose, and that he will not be able to participate in the defining event of his generation, the war.
Dr. Stanpole tells Gene about Finny that
"Sports are finished. As a friend you ought to help him face that and accept it. The sooner he does the better off he'll be".
When Gene hears this, he
"burst(s) out crying into (his) hands...(crying) for Phineas and for (him)self and for this doctor who believe(s) in facing things".
Gene understands that the doctor has no idea of the magnitude of the difficulties that Finny will have to face. Gene is tormented by the guilt of the realization that he had purposely jostled the branch and made Finny fall, Finny, who had just a few days earlier courageously declared that Gene was his "best pal". Finny will not only have to face the fact that he can no longer participate in the sports that he loves, but that the reason for this tragedy is a betrayal by his self-proclaimed best friend. Also, although Gene does not yet realize the full implications of this, Finny will have to also face the reality that while all of the others will be swept away into the tide of war, the defining event of the day, he, who has always been a leader, will alone be left behind (Chapter 5).