From Eugenia Cheng's Beyond Infinity, Chapter 4:

Mathematics can sometimes seem like a process of never getting anywhere, because every time you work out something new, it just reveals all the other things you don't know. And it's hard to keep track of where we've come from, because once we understand something, it can be hard to remember how difficult it used to be. I often feel like I'm making no progress in math because everything I already know seems easy and everything I haven't done yet is difficult (otherwise I'd already have done it).

^z - 2017-07-30