Don't we all had moments in our learning path, leading to self discernment "I wish someone would told me this before I started!" or "Learning would be so much easier onward if I first knew this!"?
To me, I wish I first knew how the request-> response cycle works, their methods, status codes and the overall process the page is being rendered.
Instead, I was just blindly typing html, css and js, without knowing nothing about what's actually happening under the hood. Stuff just 'magically' happened to me.
So, what about you? What did you learn the hard way?