i started professionally in 2001, however I was programming in DOS in the early nineties. The biggest lesson I learned, besides never stop learning, is that if I put my mind to it, I could do just about anything thrown my way, and that I was extremely adaptable to picking up new projects and running with them. That transitioned over to other aspects of my life, and gave me more confidence as time went by.
For years I struggled with "Imposter Syndrome", and because I also seemed to start off at jobs working in classic asp (a predecessor to .NET), I didn't think I was "doing it right". Eventually I learned front-end work, as well as databases, and eventually became a full stack developer. When I got feedback saying "wow, how'd you do that in such an archaic language?", I simply smiled. This wasn't about stroking my ego, but rather showing me that I could do something not everyone can do. As someone with a disability, this really boosted my confidence, and like I said earlier, helped me with other aspects of my life :)