This article is a great source of information for young people who still are at the start of their life. But for the OP and for us older ones, instead of saying

This article is a great source of information for young people who still are at the start of their life. But for the OP and for us older ones, instead of saying "what could I have done better?", it's better to say "what should I do better today". This is because a lot of things that could have been done better don't matter now anymore. Instead, use the knowledge learned from looking back to the past to improve your future. The only thing I disagree with though is to define a clear education and career path. It's always easy to say that in hindsight, but if you are at the start of the path and already fix your destination then, you are closing off a lot of opportunities. I've seen people who had a very clear goal at the start of their career, and then burn out because that goal turned out to be not obtainable, and I think they would have been happier if they cared less and just switched to more obtainable goals as they went along.