I have learned from being a parent and from working in healthcare that despite the best laid plans, you can never predict how your life could change in an instant. So I have learned to go with the flow during the course of my days. I still do some planning, by looking ahead at my schedule in the upcoming days and weeks, so I can be prepared physically and mentally for the upcoming events.
As for schoolwork and other tasks and responsibilities, everyone has their own style. Some prefer the structure of being highly organized and keeping a handle on things; other people (myself included) tend to put things off and pull things together at the last minute. It’s up to you to find out what works best for you.