The 10-3-2-1-0 rule is a popular sleep-hygiene shortcut rather than an official clinical guideline. It aims to taper stimulation before bedtime: stop caffeine 10 hours before sleep, avoid alcohol/heavy meals 3 hours before, stop work/mental load 2 hours before, turn off screens 1 hour before, and hit snooze 0 times. For many people with irregular routines, it creates a clear behavioral runway into sleep. Scientifically, the core targets are circadian support and conditioning: consistent wake time, morning light exposure, reduced evening light, a cool/dark/quiet bedroom, and using the bed only for sleep and intimacy. In chronic insomnia, these are often elements within CBT-I, and a simple rule may not be sufficient on its own. Think of 10-3-2-1-0 as a strong starting framework—if insomnia persists, structured CBT-I and medical evaluation are appropriate. Evidence base: guidelines naming CBT-I as first-line; trusted reviews on sleep hygiene/circadian principles; references describing 10-3-2-1-0 as a sleep-hygiene method.