睡眠：尽管睡足八个小时，六点半起床我感觉糟透了，而八点起床就好极了，这时为什么

Even if I get 8 hours of sleep, if I wake up at 6:30 am, I feel terrible. If I wake up around 8 am, I feel great. What's going on?This has always been true of me—when I'm in the habit of getting up at 6 AM, I always feel tired and burnt out.  But when I'm in the habit of getting up at 8 or 8:30 AM, I consistently feel energized. What's going on?Farah Ghniem, I struggle with early mornings.Written Sep 27Sadly, biology dictates a lot when it comes to sleep patterns. I’ve spent years trying to turn myself into a “morning person”. Due to my current job and commute, I have to wake up no later than 6:30 am every day. This may not seem so late to some, but despite everything I’ve tried and continue to try, this makes me chronically tired and constantly feeling like I’m not getting enough sleep, even if I go to bed earlier and increase the number of hours of sleep I get.We all seem to be happy with a certain number of hours of sleep; this is socially accepted and if you ask around, most people will tell you their number. Those who need less sleep will often wear it as a badge of honor and rub it in your face, raising incredulous eyebrows at you if you dare to say something like, “oh, no, 4.5 hours only would leave me destroyed.”But there is something else. We are also all genetically /pri:dɪs'pəʊzd/  to needing our hours ofsleep in a certain “slot” in the night. This is better known as our“chronotype”, and it is defined by our “midsleep”. Simply put, midsleep is thehour in the night when you’re halfway through your required number of hours intheir / ˈɒptɪməl/ /pə'zɪʃnɪŋ/ within time. You can figure this out if you have a bunch ofdays off. Go to sleep when your body is compelled to, rise when you feelrested. Take the number of hours you slept, divide them by two and add theresult to the time at which you fell asleep. That’s your midsleep orchronotype. A lot of us aren’t getting our sleep when we need it, due to 8–5 or9–5 work schedules, resulting in chronic exhaustion that mimics jet lag thateven has a term coined for it: “social jet lag”. To learn more about this Irecommend a book called Internal Time by German chronobiologist Till Roenneberg.Early chronotypes will of course also rub that in your face: “I just open my eyes at 4:30 am and smile and begin singing with the birds and butterflies.” Early chronotypes who need few hours of sleep? They’re probably plotting world domination. It is a bit of a genetic lottery, this one.One thing that has made early mornings less painful for me is exercise the previous afternoon/evening. Another is having married a morning person who brings me coffee to bed so I can wake up faster. I highly recommend the latter!Perhaps more things will work for you. Good luck! Society really perceives late chronotypes as weak-willed and lazy and 8–5 work schedules can be unforgiving for those of us who need those early morning sleep hours.