What time do you go to bed? What time do you usually get up?
Personally, I always go to bed around midnight. I try no later than 00 hours. I usually get up at 7.00 at the alarm clock. On weekends I can sleep until 9 o'clock in the morning. If I sleep less than 7 hours, then I walk like a sick person all day. So 4 hours of sleep is not for me.
Getting mature will make us Less sleeper , because of so much things to think and done, 4 hours sometimes is Long enough for the night and just take a Nap in the afternoon at least 1 more hr.