In judo you always know how good you are. Someone throws you or they don't. There's a scoreboard. There are belts, you can see what you've earned and what's next. You lose in public constantly, in front of everyone, and nobody thinks less of you for it; that's just training. And the first thing they teach you isn't how to throw someone. It's ukemi how to fall without getting hurt. You spend months learning to be thrown before you're allowed to attack.
I did that for years, professionally. Then I moved into tech, sports science, then game development, then cloud security and every one of those things was gone.

Here's what took me years to work out, and it's the whole talk: impostor syndrome isn't a personal defect. It's what happens when you take a person out of a system with feedback and drop them into one without any. Tech has no scoreboard nobody tells you if you're good. It has no belts progression is invisible and the titles don't mean the same thing at two companies. Failing in public isn't training here, it's a performance review. And nobody teaches you ukemi. You're expected to attack from day one, and when you get thrown you have no idea whether that's normal or whether you're finished.
Four things judo had. Tech has none of them. That's the diagnosis, and I'll go through them one at a time.
I wrote a book about this, which means people wrote back engineers, career-changers, people ten years in. The thing that comes up over and over: everyone assumes they're the only one, and they're all assuming it about each other.
Then the fix, which isn't confidence. Confidence advice fails because this isn't a confidence problem you simply have no data on yourself, so you fill the gap with the worst available assumption. So build the missing structures yourself. Make your own scoreboard: an actual file of what you shipped and what you fixed, because your memory won't do it for you. Learn ukemi deliberately practise failing where it's cheap, so you know how it feels before you fail where it's expensive. Find your randori: somewhere you can be thrown regularly without it counting against you.
I got thrown more times than I can count and never once thought I didn't belong on the mat. Falling was the training, not the verdict. Tech taught me to read the same event as proof I was a fraud. That's the mistake, and it's worth naming out loud.