To establish a particular atmosphere, mood, or tone, you must pay attention to your readers’ short memory for sensation. If the atmosphere is to be foreboding, you must forebode on every page. If it is to be cold, you must chill, not once or twice, but until your readers are shivering. Remember that you’re creating an experience, not just imparting data. Sensory information once said is not enough said. Our own experience tells us that a hangover is a constant presence for its full duration no matter what else we are doing. Don’t be afraid of repetition.