How is "The Last Leaf" by O. Henry a story of hope, friendship and sacrifice?

O. Henry's "The Last Leaf" is a story of hope, friendship, and sacrifice because Sue and Mr. Behrman do not give up on restoring Johnsy's will to live. Instead, they offer their loving efforts to help Johnsy regain her health, and Mr. Behrman even sacrifices his life for Johnsy.

Johnsy, who becomes ill with pneumonia, speaks despairingly of the leaves outside that drop from the vine because of the icy weather. In her despair she tells her roommate and friend Sue that she "must go, too." Sue rejects this despair, saying,

"Oh, I never heard of such nonsense... What have ivy leaves to do with your getting well?"

Sue further offers hope by lying to Johnsy and telling her the doctor says her chances of getting well are "ten to one!" and that is as good a chance as they have when they ride on the street cars. To change the subject and be more encouraging, Sue then urges her to sleep.

• Friendship

When Johnsy suggests that Sue sketch in the other room, Sue declares her friendship, saying she would rather be with Johnsy and stay in the same room with her.

After she tells Johnsy she will be back in a minute, Sue rushes down to Mr. Behrman, who she knows cares about Sue, and informs him of Johnsy's growing hopelessness. Hearing of this despair, Behrman becomes angry and changes his mind about not posing for Sue. Instead, he accompanies Sue to the girls' apartment where Johnsy is now sleeping. Sue and Behrman look out the window.

Then they looked at each other for a moment without speaking.

Behrman sits down and poses for Sue; later, he returns home.

Old Behrman, who has said nothing about what he has seen out the window is found two days after the night he has posed. He has died in the hospital having fulfilled the scriptural words of John 15:13 (King James version):

Greater love hath no man than this, that a man lay down his life for his friends.                        

Behrman went into the icy night, climbed a ladder, and painted an ivy leaf so Johnsy will not know all the real leaves are gone. Behrman's leaf has restored hope to Johnsy and makes her determined to get well.