Identifying the Central Theme in 'The Gift of the Magi'

In the short story "The Gift of the Magi" by O. Henry, a young couple, Jim and Della, are deeply in love and wish to give each other meaningful Christmas gifts. However, they are poor and don’t have enough money to buy the perfect gifts. Della decides to sell her beautiful long hair to buy a platinum chain for Jim's prized possession, his watch. Unbeknownst to her, Jim sells his watch to buy a set of combs for Della's hair. When they exchange their gifts on Christmas Eve, they realize the irony of their sacrifices—a poignant lesson about love and selflessness.