Another quotation from May Sarton's The Small Room:
"... she caught herself wondering whether crisis may be one of the climates where education flourishes--a climate that forces honesty out, breaks down the walls of what ought to be, and reveals what is, instead."
I marked this because I think it applies to writing as well as education. And I'm not thinking about the writer's crises here (although I suppose that could apply), but the characters' crises. At the heart of any story is conflict, the conflict that "forces honesty out" and shifts the worldviews of the characters. It is in crisis that characters confront their weaknesses, and fall prey to them or grow past them. In crisis, they often face things they've been trying to ignore.
At the climax of a story, there is an honesty, a revelation of "what is," and this moment is the reader's payoff. At this moment, we discover whether the hero is stronger (or wiser) than the villain; we learn whether the character belongs with her love interest; we find out the secret the main character's been hiding; we solve the mystery. We see whether the main character is going to put on his big-boy pants and grow up. We see whether he has the internal strength to cope with an external defeat.
Crisis gives life to a plotline; it breaks open characters to reveal the hearts within.