When I was in high school, I honestly had my schedule down to a science. My school day was perfectly timed for me, I was able to be in five clubs a week, school musicals were extensively planned months in advance, and my work schedule was fairly consistent, as my boss had all of those other listed activities in place to work around.
Then college happened.
I now have classes all over the place, and so technically more free time. So, why not work full time? I also got into a real relationship for the first time in my life, and was really in charge of taking care of myself. Surprise surprise, I had absolutely no "real" hobbies anymore. In high school I had clubs, musicals, and hanging out with friends to fill my time - all of which seem to fizzle out during my college experience. And so I overloaded myself with new time fillers and became overwhelmed. I didn't think about the true time commitment that came with full time school, full time work and a full time relationship with someone who lived an hour away from me. But I was able to do what felt like so much more in high school - what changed?
Then I realized the importance of keeping a tight, concise calendar. The only reason I was able to work such a balancing act in high school was because I knew exactly what I was doing, and when I was doing it; and all of that was planned for me by someone else. I then expected the same out of myself in a brand new, much larger environment, where no one was handing me a well thought out, cohesive schedule. My psych teacher didn't care if class ran into a club meeting I wanted to attend. My boss didn't care that I took on a new eight week class midway through the semester that I forgot to write down when I applied. I was very suddenly in charge of my time in a way I never had been. I overbooked myself, and ended up dropping out in only my second semester and had to take a month or two just to recollect myself.
But no worries! All is well now and I am on track to graduate in the fall of 2022. But that's only after completely reevaluating how I treat myself and my time. So, in short:
Be able to realistically estimate how much time a new hobby/interest/job/relationship/etc. is going to take out of your week. Currently, I am in the last weeks of an internship that was about 20-25 hours a week, have another job that's about 10-15 hours a week, am in the last legs of two summer classes, take care of approximately thirty houseplants, love to bake and cook, still manage to keep my living space clean and my partner happy, and also just began cycling a brand new fish tank. Oh, and just re-took up writing.
I have been keeping a "normal" calendar to look ahead at future events, and also keep what could be considered a "past calendar," but I call it my time journal. Over the past two years, this has helped me look back and figure out: what went wrong this week? Was I overbooked? Under? What from the past few days might have made me feel the way I do? What can I do to change that? In all honestly, my time journal is way more effective than my traditional calendar in terms of my mental health. I feel really good looking back at what I have accomplished, and can better estimate what new hobbies I can realistically add into my life.
So if you're in high school, and you're just getting your schedule for this next fall semester sent to your inbox - just remember that it will soon be your responsibility to plan all of that out; it won't come wrapped all neat and tidy for you. Practice planning, looking ahead, and especially looking back. Log the good and the bad, and see what you can do to optimize not only your time, but your happiness. The longer you do it, the better you will get at it, and the happier you will be.