A reader writes to author Annie regarding feeling used to be a friend who attends birthdays, check in after surgeries, brings soup when someone is sick, and sends the "just thinking of you" text. However, lately, she has noticed that when she is the one having a difficult time, her friends become silent. This has led to her pulling back and feeling resentful. How do you know when a friendship is worth saving versus when it is time to let it go?