This is a very good question and I have some suggestions based on my own experience.
A really good way to reduce your stress in balancing all of your activities is to ensure that you have your time as organized as possible. Find something to write out your week on - this could be seven index cards, or a large calendar, or a plain sheet of paper with lines on it. Do this preparation work on a Sunday evening or whenever your mind is relatively calm, and write out everything you know you have due for each day of the week. Review your syllabi from your classes and include any social activities, club activities, work commitments, etc. Once you have everything in your week written out, you can then figure out when you will have time to get all of your work done, and create blocks of time to achieve. This will also help you spot conflicts ahead of time so you can resolve them.
If you have a tendency to get distracted during your day and you have a smartphone with a calendar on it, use the calendar to set reminders so that you do not forget where you need to be and when. Ensure that you get enough notice in your reminders (if it takes 15 minutes to get to your next class, set a reminder 30 minutes ahead of time).
After you have your week organized, do the same for the following week, and even the next week. You may not know everything you have to do a few weeks out, but you can always add as you go. Always to a week-ahead review on Sunday night to ensure you have the known items convered.
Once you have your week organized, then every night before you go to bed, be sure to review the next day's required work. You can even review your whole week if you have a few minutes to do so. This will help you recall what's on the schedule for the following day, remind you of what you need to get done and help your mind feel more comfortable that there will be no surprises. Your brain will be able to relax better when it's not struggling to keep track of everything.