You cannot safely sleep 8 hours of true sleep in 4 hours
Use a consistent sleep schedule every day
Go to bed and wake up at the same time
Reduce caffeine, nicotine, and alcohol
Avoid screens 1 to 2 hours before bed
Keep your bedroom dark, quiet, and cool
Get bright light exposure in the morning
Exercise regularly, but not right before bed
Avoid heavy meals close to bedtime
Use a short nap if needed, ideally 10 to 20 minutes
Prioritize sleep quality over trying to compress sleep
If you feel unable to function on little sleep, seek medical advice