As a college student with a difficult major and two minors, my timetable is my best friend. It's not an exaggeration when I say that I live and breathe by it. I don't schedule anything without looking at it, and if anyone (friend, professor, boss, etc.) asks me, "Do you have free time at [X]?", I just email them a copy of it.
If you don't have a timetable, then that might be why you can't seem to manage your time properly. And I don't just have my classes scheduled. Every single thing I ever have to do is logged in it. This includes, but isn't limited to :
- Work study
- Work (outside of work study, like here!)
- Meal times
- Homework times (further divided up by class)
- Tutoring appointments (for me and my classes)
- Extracurriculars (the number of which has shrunk as my college career has gone on)
- Cleaning the apartment
- Me time (because who can live without down time?)
- Sleep time
Now, when I mark down time in my time table, I also include any extra time that might be necessary. For example, if I'm setting aside time for math homework, I'm definitely going to be setting aside at least twice as much as I set aside for religion, because I know that math historically takes me more time to do than a 40 page reading.
I used to just play everything by ear. "I have time right now, so I'll just do [Z] now." While I can still get things done, I don't necessarily get the important things done. By putting literally everything into a schedule, I have a strict routine that allows me to accomplish absolutely everything. Now, I recognize that this kind of organization is not for everyone (and scheduling even meal times can seem a bit odd). But people thrive on routine, and I guarantee if you try setting a timetable for yourself (which doesn't have to be as nuts as mine), then your productivity will improve.