Why do I feel more tired when I sleep more?
Every night, an average person goes through five sleep cycles. Each of those cycles takes around 90 minutes to complete. Five 90-minutes add up to 450 minutes in total, or nearly 7.5 hours. The stage of sleep at which you awaken has the most impact on what we call a sleep hangover.
There are five stages: stage one, stage two, stage three, stage four, and REM. Phases one and two are the simplest to wake up from, and REM is somewhat more complicated. Phases three and four are the most difficult. When you sleep an added few hours than you usually do, you’re more likely to wake up from the REM cycle, or cycles three and four, which makes you feel groggy.