That could do it. An extra half an hour will put you right in the middle of a sleep cycle. If you wake up in the middle of one, you will feel tired. There are people who will only go through one sleep cycle at night and one in the middle of the day. Their total sleep time per day is less than 2 hours, but they have to be very much on schedule, if they miss one or sleep in too much, their day is ruined.
That could do it. An extra half an hour will put you right in the middle of a sleep cycle. If you wake up in the middle of one, you will feel tired. There are people who will only go through one sleep cycle at night and one in the middle of the day. Their total sleep time per day is less than 2 hours, but they have to be very much on schedule, if they miss one or sleep in too much, their day is ruined.
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