Exactly. I had to double up on classes and take some subjects on my own over the summer. Two classes one semester literally overlapped by about fifteen minutes

Exactly. I had to double up on classes and take some subjects on my own over the summer. Two classes one semester literally overlapped by about fifteen minutes and I had to get special permission to show up late for it. I got a passing grade for it, but finished it afterward. It wasn't a matter of being super-human, just loving the subject. I agree, though, that if your passion isn't overwhelming, you can't do it. You can with many non-STEM majors. The first couple years of graduate school were brutal. I had taken twenty math and science classes undergrad. Typical Russian and Chinese classmates had taken thirty to fifty and they blew me out of the water. The one guy in the program who took nineteen courses dropped out, so I was right on the border.