The first computer I had access to was my family's Windows 95 PC. I learnt to write HTML in notepad and see it rendered in Internet Explorer. This was the beginning of my career, but so much of what was happening was accepted by my brain as simply "magic".
I would later chip away at that stack of magic and learn how more and more things worked, but even while being an accomplished programmer I still had this feeling that magic existed. It wasn't until I learnt to build my own computer from discrete logic components (thanks, Ben Eater) that I finally felt like I understood it. Computers are just machines.
I've since revisited textbooks (like Knuth) and the history of computing (starting with Babbage) and feel like my eyes are no longer obscured by my preconceptions about what a computer is.