I was a night owl, used to stay up even when working, I remember the first episodes of Prison Break, I used to stay up for that - I was able to work flexi time. I used to get my clothes out the night before and shower and wash my hair.
In the morning I'd go back to sleep after hubby went off at 7.30am, wake up at 9am, jump out of bed, downstairs, soak oats in milk and make a tea, let dog out, back upstairs, quick wash and dress, downstairs, eat oats standing up and finish tea. Let dog back in. leave at 9.20 and arrive at work at 10am, bright and breezy had nothing on me, always a skip in my step, if I'd slept well. I used to stay until 6.30/7pm to make up hours and avoid the traffic.
I loved my job and colleagues. but allowing me that freedom of not having to get up at 7am meant it also helped me to avoid the fact that I wasn't really well for a few years. Ignore your body clock at your peril.
Being sick means your illness over-rules your body clock to a degree but the basics are still there and I still feel better if I stay in bed until say 10am, especially if I've stayed up a bit later the evening before. Going to bed at 10.30pm sucks but its what I have to do now.