Frankly, the biggest mistake of my career thus far has been starting it. I didn't get in to a university, so I bumbled around for 6 years at a community college. In the middle of it, I managed to get a 6-month stint at a help desk (which I needlessly proud of, and then promptly fired from). Went back to the community college, burned out on trying to get an associates and transfer, and tried changing course to getting some sort of certification. Ended up with a CCNA (which expires later this year), but it turns out nobody near where I live wants to hire a network technician or engineer without a diploma, and my savings aren't enough to move.
So now I'm in my mid twenties and I've only just managed to get an (unpaid, remote) internship thanks to a sympathetic small business owner whose pet technical project is falling behind schedule. Every time I open the project management tool, I feel a vague sense of unease because I'm socially tone deaf and I can't tell if I'm breaking some unspoken rule about "don't word this message this way because you'll sound too confident for an intern speaking to the senior developer," or "don't make a comment on this task because it's assigned to an intern on a different team and you're not supposed to go out of your lane."
I've been writing code of some sort for 11 years, and using Linux daily for 8. Every day I wake up in my childhood bedroom and send my one remaining friend a message. Sometimes she even replies. Then I have the pleasure of spending most of the day fighting with some stupid self-inflicted issue, like why Ethernet broadcast breaks every week on OpenWrt, or why Pulseaudio uses 200% CPU when I try to get it to communicate with a certain cgroup, or what I'm going to use when Fedora 33 hits end of life and I have to get some other DE set up to replace GNOME.
I've dug myself into a labyrinthine, unsatisfying, inescapable hole. So if I could do it all over again... I wouldn't, because, like a ball on a hill, I'd end up right back in here.