What separates top tennis players? Their power, skill, talent? Nope. How they manage their downtime, the time between, games, sets and matches. Those that chill, relax and refocus always beat the one stamping and pacing and berating himself between points.
In a world of unpredictability time is something you can never manage perfectly. You're always going to be late or early, or have your time 'wasted', or be trying 'to do too much'. Time management is always a kind of fantasy. Even when people only do so much per time slot, never over running, they are in fact managing energy not time.
I know from writing if I allow a two hour slot only, I'll get more done than an open ended 'do as much as I can' set up. The time constraint makes me focus my energies. But if I then get greedy to do more I find the next day I can't get anything like as much done. By finding the optimum energy concentration slot I maximise my output.
A good soldier always sleeps whenever he can- he never knows when he won't be able to.
You can a manage your energies very precisely. It is entirely within your own control how much you bring to the party, or how you choose to relax. By focusing on managing your energies you regain a sense of control over your own destiny.
Time can't be owned with anything like the same precision. And if you are normal you will want to 'give time' to others. Well that can't be budgeted in so you either accept your timetable is shot or be ungenerous to others.
The function in Zen Buddhism of a very precise timetable is not to lock the monk in. On the contrary if anything important comes up a monk is free to depart from his set routine of work and meditation. The timetable is there for when there ISN'T anything 'important'. It's there so that you always know what you should be doing, you're never at a loose end dribbling away your energies.
Energy needs a focus or framework to be maintained. Think of a pipeline with loads of holes in it- only a fraction of the water pumped in arrives. That is what happens when you start with energy and no focus, no framework. The energy doesn't build. But if you have a time constraint or a very specific achievable target you have a pipe with no holes. Energy is maintained as momentum- that carries you on to the next thing you want to do that day.
We can be tyranised by a timetable instead of using it as an aid to energy maximisation. Use the timetable to construct slots that allow for maximum output. Don't try and 'get as much done as possible' treating yourself like a knackered horse pulling a cart, instead plan the day so your energy builds and does not wane. Think of those formula one drivers who have to ration their fuel so as not take badly planned pit stops.
A hi-energy encounter can be a 1000% more successful than a low energy one, or a wrong energy one. Use your time to manage such energy.