"The years of Sara Emanu's life were all equally good." Yet, for ninety years Sara suffered the pain of not having children. If so, how could she consider that all the years of her life were "good?" The tzadikim know and firmly believe that any hardship they experience in this world serves as a purification.
Lesson: Although Sara suffered many painful years, Sara considered them all "good" because the difficulties cleansed and purified her.
App: Instead of perceiving hardships as "bad," reframe them as healing bitter medicine that makes us worthy for Gan Eden.
[Based on the commentary of Rashi and the Darkie Mussar]
