Majoring in any aspect of music is difficult. While the rest of the university gets 3hr courses that require little work (on the lower levels), you will have 1 and 2hr classes that require a lot of work. The trick is to find a way to enjoy it, such as listening to music history pieces with a group of classmates.
As far as time management specifically: make a schedule. Use Excel to make a spreadsheet of all 24hrs in all 7 days. Schedule classes, work, sleep, studying, and practicing. But also schedule fun time. You can color code it as well. Schedule free time. Whatever you feel you need. Some things, such as classes, are fixed time. But if you schedule practice time at 7am and keep waking up too late, move it. Make the schedule into something that works for you. I did this in college and in grad school and in the work force, but it changed many times as I got older and my work preferences changed.
When you become a music director, the same can be used for your work days. If you decide to change majors, the same would work if you're in marketing too. College is where you truly learn when you are most efficient and in what order you can perform different activities and be efficient. Don't stress out over it, just be you and aim for being hard working and efficient. Good luck!