Sleep efficiency—the ratio of time asleep to time spent in bed—is one of the most actionable sleep metrics. Unlike subjective sleep quality ratings, which vary wildly between individuals, sleep efficiency provides an objective measure of how well you're using your time in bed. Values above 85% are considered normal; below 80% may indicate insomnia or other sleep disorders requiring attention. Improving sleep efficiency often produces more restorative sleep without necessarily increasing total time in bed. The most effective sleep efficiency intervention is sleep restriction therapy. The counterintuitive approach: spend less time in bed, not more. By limiting bed time to actual sleep time plus a small window, you increase homeostatic sleep pressure, fall asleep faster, and sleep more consolidated. Once sleep efficiency improves to target levels (85%+), the sleep window gradually extends. This CBT-I (cognitive behavioral therapy for insomnia) technique is evidence-based and often outperforms medication. Time-in-bed misconceptions lead many people to spend excessive time in bed attempting to sleep. If you lie in bed for 9 hours but only sleep 6, your sleep efficiency is 67%—poor by any measure. The bed has become a place of frustration rather than sleep, creating conditioned arousal that further impairs sleep onset. Reducing time in bed until sleep becomes consolidated resolves this conditioning and restores bed as a sleep cue. Stimulus control therapy addresses the conditioned arousal that develops when bed becomes associated with wakefulness. The rules are simple but require discipline: use bed only for sleep and intimacy; if you can't fall asleep within 15-20 minutes, leave bed and return only when sleepy; maintain consistent wake times regardless of previous night's sleep; avoid naps if they're interfering with nighttime sleep. These rules break the association between bed and wakefulness and restore its sleep-promoting properties. Sleep environment optimization directly impacts efficiency. A bedroom that's too warm, too bright, or too noisy prevents continuous sleep. Even minor disturbances—room light penetrating curtains, a partner's snoring, ambient temperature slightly above optimal—fragment sleep and reduce efficiency. Targeted improvements to these environmental factors often produce measurable efficiency gains without any other behavioral changes. Cognitive factors—worry, rumination, anxiety about sleep itself—fragment sleep by preventing the mental quieting necessary for sleep onset. Cognitive therapy techniques help identify and challenge dysfunctional beliefs about sleep ("if I don't sleep 8 hours I'll be useless tomorrow") and develop healthier relationships with nighttime worry. Worry journaling before bed—writing down concerns and tomorrow's tasks—externalizes the cognitive burden and allows more peaceful sleep onset.