Besides the subject matter of my classes, here's what I've learned this past semester:
1. Don't bite off more than you can chew.
I was sure I could take 15 credit hours of classes and work 20 hours a week for the semester. I was wrong. I managed to stay afloat until the very beginning of November, but looming coursework after that time proved to me that I wasn't as resilient as I fooled myself into being. After dropping my Differential Equations class, I felt liberated and was able to spend enough time studying for my other classes. I therefore will not take more that 6-8 credit hours of difficult math/physics courses if at all possible for the remainder of my college career, and will do my best take no more than 14 credit hours total as long as I am working 20 hours a week.
2. Perfection is too high a standard.
I believe I will get decent grades this semester, but I will likely miss my perfect straight A semester I planned for myself before the semester began. That being said, I feel I learned the subjects I finished well enough to continue my career, and will do my best to keep it that way for the rest of this one.
3. Improvement is a lifelong process.
This seems like an obvious one, but to me it was a timely revelation. I cannot expect myself to be where I want to be without a little work, and sometimes that work spans over months, or even years.
4. Have fun.
No matter how much I like physics, I occasionally need a little time away from it.
That's all I can think of at the moment, maybe I'll come up with something else later.