It became quickly very clear to me in undergrad that some people had this intuitive conceptual understanding of math and physics that I would simply never have, despite the effort (and I did make good grades). Some of these guys just blew me away with how smart they were. The more time I spent around people a lot smarter than me, the more I realized that some people's brains are just operating at a completely different level. I could have done physics, but I never would have been doing cutting edge theoretical research. I'm simply not smart enough. There is quite clearly a spectrum of mental capabilities from mentally challenged all the way to genius level. To believe this has no impact on what you're capable of achieving in a lifetime is quite naive.

And you would not have been doing me any favors by trying to convince me that I could have had a meaningful career pursuing theoretical physics research, something I'd never realistically achieve.