To me, transistors are the best example of how hard EE can be. I heard "transistor is a switch" or "transistor is an amplifier". So I bought some MOSFETs and tried to use them. No go. Well, I had to learn (through random web pages and some books) that microcontrollers struggle to switch mosfets. Fine. I'll get a gate driver. Then I have to very carefully pick a bunch of resistor values that make my system behave. Eventually, I learn that transistors aren't switches at all, but can be coerced into sort of behaving like switches, but in reality, there is always leakage and a hundred other variables you have to understasnd and control for. You can see one of my threads here: https://www.reddit.com/r/AskElectronics/comments/1omqn4d/con...