In reading some stuff on this forum and about general math education in the US at least, I'm curious as to others' experience with math and when it "got hard" for them. People here I assume are mathphiles and love math. They've done well, math came easy, etc. I include myself in this category. But there came a point for me, and I think it comes for everyone, where math becomes more work and hard. For me it came when I took differential geometry. Everything before that - Calc I-III, Linear Algebra, Differential Equations, etc. came pretty easy. I took all honors courses and got all As. I had to work, but I never found it very difficult. When I took differential geometry, I felt I was a bit out of my element. I struggled, but ultimately did well. But it was an awakening. Looking back, I can't pinpoint exactly why. Maybe my smarts had reached their limit. Maybe the material I had studied before was not rigorous enough or sufficient enough to prepare me for that course. I feel more the latter. Looking back, even the honors courses were more computational-based than theoretical. Even the books used. And the transition hence was not a smooth one. But I could just as easily be rationalizing this and maybe I DID hit a mental block. Before that I could just read the books on my own, do the work, and get As. After that I had to work with others, ask more, book reading was not as easy and natural, etc. Was it a case of insufficient material leading up to it, my brainpower, or both? I still don't know, so am curious to hear other stories. Because I do think everyone hits a sort of wall at some point.