I never doubted that I enjoyed programming, because I kinda fell into it while avoiding homework and only after much resistance decided to make it a career.

I did have a lot of doubts about whether I was good enough at it to make it as a career. And that continues, basically every time I'm faced with a hard problem, even though I'm now a mid-level Area TL at Google responsible for software that hundreds of millions of people use. That's the nature of software (and innovation in general): before you've done something, other than the most trivial problems, you wonder whether you can do it, and then once you've done it, it's done and you move on to bigger challenges.

I would basically stop thinking in "rest of your life" terms and start thinking 2-3 years down the road. Are you happy doing what you're doing? Is there something else you'd rather be doing? Are there any particular developments that make you excited? Answer those questions first and that'll give guidance to shape the rest of your life.

I have no idea what the world will look like at the end of my life in hopefully ~40-50 years (who knows, I could get COVID and die next month). I suspect that demand for software engineers will be a lot less than it is now. But there's also a whole bunch of tail risks we're certainly underestimating - the U.S. might break up into lots of tiny little states, Russia could roll through all of Europe, we might all be underwater from rising sea levels, whatever. It's not worth worrying too much about them. Worry about the risks you're going to face in the next couple of years and trust in your ability to adapt beyond that.