of sleep be obtained at night instead of through napping, because while naps can be helpful after sleep deprivation, under normal conditions naps may be detrimental to nighttime sleep. Negative effects of napping on sleep and performance have been found to depend on duration and timing, with shorter midday naps being the least disruptive. There is also focus on the importance of awakening around the same time every morning and generally having a regular sleep schedule. Activities Exercise is an activity that can facilitate or inhibit sleep quality; people who exercise experience better quality of sleep than those who do not, but exercising too late in the day can be activating and delay falling asleep. Increasing exposure to bright and natural light during the daytime and avoiding bright light in the hours before bedtime may help promote a sleep-wake schedule aligned with nature's daily light-dark cycle. Activities that reduce physiological arousal and cognitive activity promote falling asleep, so engaging in relaxing activities before bedtime is recommended. Conversely, continuing important work activities or planning shortly before bedtime or once in bed has been shown to delay falling asleep. Similarly, good sleep hygiene involves minimizing time spent thinking about worries or anything emotionally upsetting shortly before bedtime. Trying purposefully to fall asleep may induce frustration that further prevents falling asleep, so in such situations a person may be advised to get out of bed and try something else for a brief amount of time. Generally, for people experiencing difficulties with sleep, spending less time in bed results in deeper and more continuous sleep, so clinicians will frequently recommend eliminating use of the bed for any activities except sleep or sex. Foods and substances A number of foods and substances have been found to disturb sleep, due to stimulant effects or disruptive digestive demands. Avoiding nicotine, caffeine (including coffee, energy drinks, soft drinks, tea, chocolate, and some pain relievers), and other stimulants in the hours before bedtime is recommended by most sleep hygiene specialists, as these substances activate neurobiological systems that maintain wakefulness. Alcohol near bedtime is frequently discouraged by clinicians, because, although alcohol can induce sleepiness initially, the arousal caused by metabolizing alcohol can disrupt and significantly fragment sleep. Smoking tobacco products before bed is also thought to reduce one's quality of resting by decreasing the time spent in deep sleep, leading to sleep fragmentation and nocturnal restlessness. Both consumption of a