I didn’t have a good experience on my last first day of school, so I’m really worried about this years. Is there anything I can do to deal with nerves?

Absolutely. It sucks that your last experience wasn't fun, but you can definitely make this next one better. Try organizing all of your stuff and picking out your outfit the night before so you don't have to scramble in the morning. Set your alarm for an hour or so before you need to be at school so you have time to shower, eat breakfast, and do your hair and makeup (if you wear makeup). Remember that your first day is usually mostly about meeting your teachers and learning about your classes, so don't stress about having to do lots of schoolwork. It'll be over before you know it and you can chill out at home when you're finished.