Take it from a girl who loves to be over involved and spread herself as thin as can be—managing time is hard and in itself takes time. These simple steps will aid your frustration of being an over-achiever like myself. There is nothing wrong with wanting to be involved and doing things, but there's no reason to stress yourself out.
1. Buy a calendar.
It doesn't matter if it's big or small or is cat themed, a calendar will help you organize your commitments and obviously help you remember when things are.
2. Eliminate things that take your time if you don't enjoy them.
Maybe that club sounded like a solid idea at the time, but its okay to stop going if it doesn't interest you and you could be doing other things.
3. Leave time for relaxation.
If you feel like every moment has to be filled, make sure one of those time slots is for a nap or Netflix session. You will be able to perform in other activities much better with a little rest.
4. Prioritize.
Schoolwork should come first before extracurriculars and organizations. Make sure to get what you need to get done (like that project that is due in two weeks that will sneak up on you) before you start on extra stuff.
5. Make lists.
Like a calendar, it can help you remember what you need to do. Buy a cute pack of post-its and start writing down reminders and to-dos. It's better to have one thousand post-its than to forget about a meeting or printing out a paper.
6. Drink water.
This may seem silly, but being a busy person can put a lot of wear and tear on the body. If you can't always get your eight hours of rest, the next best thing is to hydrate and fuel your body with nutrition.
Good luck being you.