When I was starting out I thought I was learning.
Turns out I was just collecting opinions from people I had no way to evaluate.
I did not know enough to know what the right questions were. I did not know how to research the answers I was getting because I did not even know what I was looking for. Someone would tell me something with complete confidence and I would write it down like it was fact because I had nothing to measure it against.
Some of those notes cost me real money later.
The problem with being new is that everyone sounds credible when you do not know enough to push back. The guys with the most polished answers are not always the ones who have actually done the work. Sometimes they are just the ones who got comfortable talking about it.
I have been doing this for twenty five years. I learn more on one project now than I did in my first three years of trying to educate myself. Not because the projects got more complicated. Because I know what I am actually looking at now. I know which details matter and which ones are just noise. I know when something is off before I can fully explain why.
That only came from doing the work. Not reading about it. Not sitting in rooms listening to people talk about it. Actually doing it, getting it wrong, figuring out why, and doing it again.
There is no shortcut to that. I wish there was.

What is the most expensive thing you had to learn the hard way that nobody warned you about?