I actually loved my classical mechanics class. The professor was really good and in the homeworks he'd come up with creative problems. The hardest part was always starting. Once you could get the right setup then you could churn away like any other (maybe needing to know a few tricks here and there).
Coming over to CS I was a bit surprised how test based things were. I'm still surprised how everyone thinks you can test your program to prove its correctness. Or that people gravely misinterpret the previous sentence as "don't write tests" rather than "tests only say so much"