This question has gotten asked a lot.
"What exactly have I learned from working in this industry for over 20 years?"
I've worked with more companies over the last two decades than I have fingers, it's taken me around the world, it's let me meet interesting people, it's let me write books about topics I live but what has it really taught me?
A whole hell of a lot.
It's taught me that I never stop learning, that there is always someone who knows more than you do and you should listen to what they have to say.
From speaking at conferences with over a hundred people in the room listening to me, I've learned to be a better speaker and get to the point rather than rambling. I've also learned to keep the slide deck simple rather than going for cool effects.
From writing books, I've learned to focus more on the content rather than the code so that readers aren't overwhelmed with pages of code and no explanation.
From writing code, I've learned to keep in mind that others will probably have to work on said code at some point so keep the code easy to read.
From networking, I've met people in all fields and have learned new things that have helped me grow today.
So when you wonder what the last couple decades have given you, you can say they've given you an experience that will stay with you and help you grow.