You don't live in isolation, though. Your rhythms are internal and influenced by your environment. Your body needs regular signals from the outside world to keep you functioning on schedule. Chronobiologists call signals including social activities, food, and light zeitgebers (time givers). They keep your clocks from getting out of sync with the culture around you. With a change in the season, daylight saving's time, and even the type of food you eat, you're making adjustments each day.
Zeitgerbers are most effective when you're young. Early in your career you might even manipulate them and think it insignificant when you override biological cycles to advance. As you get older your rhythms become less flexible so your goals and habits may need to become more flexible.
When you have control over your daily schedule, make a list of what you need to do, including time to mull over events, and then look at how these activities might fit together with your body’s natural schedule.
Schedule brain intensive tasks early in the day, activities where you can engage your full self mid-day, and then late afternoon, sit and reflect on how much easier it is to work this way.