There was a time in my life when my brain didn't function beyond 10 o'clock. I couldn't think straight any longer and would head to bed. When Hubby and I married, he was baffled by my early bird rising and I couldn't understand how he could be an night-owl and stay up until midnight every night. It was a rough thing for me to accept.
I'm still an early riser and he still prefers to stay up late, but after becoming parents, we learned that our schedules were not our kids schedules. That was really rough to learn.
Now, many years later, I'm finding my best time to get anything done is after the kids are in bed. That's my best time to write, to do my school work, to bake something special, or to relax. My brain is able to think beyond the ten o'clock hour and thank goodness for that! I'd never get anything done!