Telling us to obey instinct is like telling us to obey 'people.' People say different things: so do instincts. Our instincts are at war... Each instinct, if you listen to it, will claim to be gratified at the expense of the rest.
Some people feel guilty about their anxieties and regard them as a defect of faith but they are afflictions, not sins. Like all afflictions, they are, if we can so take them, our share in the passion of Christ.
Part of every misery is, so to speak, the misery's shadow or reflection: the fact that you don't merely suffer but have to keep on thinking about the fact that you suffer. I not only live each endless day in grief, but live each day thinking about living each day in grief.