I can distinctly remember in my second or third year of engineering undergrad doing some stuff with the Radon Transform. At the time I had nothing to map it too

I can distinctly remember in my second or third year of engineering undergrad doing some stuff with the Radon Transform. At the time I had nothing to map it too. The maths to me was completely abstract. I just sat there, thought hard, and worked through problem after problem until it became intuitive. Now I have difficulty understanding what I found hard, because it all fits together with loads of other things into a coherent mass of concepts. It was interesting to me because it was one of a few times as an adult where I realised the framework was completely missing and I would just have to start from scratch, which meant lots of rote effort and thinking hard. There was no shortcut.