How to Keep Something Running
Getting something running once is easy. Keeping it running quietly for years, without having to think about it, is the actual skill.
You'll need a small machine you can reach over SSH — a spare computer, a cheap board, or a low-cost rented one — and an evening.
Anyone can get something running once. The screen lights up, it starts, it works — for now, on this machine, while you're watching it. The skill worth learning is different: keeping it running quietly for years, without ever having to think about it. That takes a different set of habits than starting it did.
Give it a proper service, not a terminal window. If something only runs because a terminal window is open and you happen to be logged in, it isn't really running yet — it's performing for you. On Linux, hand it to systemd instead: a small unit file that starts it, restarts it if it crashes, and starts it again on its own the next time the machine restarts. This one change quietly fixes most of what goes wrong with things people run "just for now."
Know exactly which folder actually matters. Decide, on day one, exactly which folder or file holds the part you couldn't recreate from scratch, and keep that separate in your mind from everything else the program touches. Everything else can be thrown away and made again without much loss. That one folder can't. Back it up like it's the only thing worth backing up, because in most cases, it is.
Check on it on your own terms, not in an emergency. Left alone, most things quietly wear down: something goes unpatched, a certificate expires, disk space fills a little more every week until one day it stops. Pick a fixed time — the first of the month, every few weeks, whatever you'll actually keep to — and use it to look for updates, check how much space is left, and read through whatever it's logged since last time. Five minutes on a schedule beats an emergency at two in the morning.
Write down what you did, while you still remember why. A year from now you won't remember which folder you meant, which choice you made on purpose, or why the one odd setting was the thing that made everything else work. Keep a single plain text file next to it — not a diagram, just a few lines: what this is, where its data lives, how to restart it, what you'd need to start it over from nothing. Future you is the person most likely to need this, and least likely to remember it unaided.
None of this is complicated. It's the difference between something you got working once and something you actually keep.