So, once upon a time, back in the ancient days of 1.12, I had a nice little survival world. I maintained it for more than 2 years and was in my early teens. It didn’t have any grand projects, but many small ones, and definitely lots and lots of love dumped into it.
However, I started that world in 1.10 and hadn’t wanted to update because I disliked the texture changes and didn’t want all my advancements gone.
I spent even more time on that world, slowly racking in even more time. Eventually tho, I with the news of update aquatic rolling in soon, I got compelled enough to at least try the at the time still new rocket powered elytra flight… so, I download the new update, open the launcher, go to singleplayer… and reflexively press my main world.
Confused and distraught at seeing all my achievements gone and seeing these deplorable so called “advancements” and all the ugly new textures, I quickly backpetal, go back to 1.10.2, open singleplayer and… hm, that’s weird, it’s dangerous you say? Well how bad could it be, definitely not worse than playing on the ugly new update. So, I load my world and… I had been parked next to an extraordinary find of a double skelly spawner, one on top of the other that i managed to get operating simultaneously, but, hm that’s weird, I’m not seeing any skellies? I stand there waiting to repair my gear… nothing. So I steel myself, go into the farm, and now they’re pig spawners. Great. I was fairly upset by this but in the end I accepted it, broke the spawners and left for the day.
Next day I log in again, go to grab some building materials from a nearby chest… nothing. In a panick I start going through all the chests in my mini storage system, and everything is gone, even the enchanted sword and enchanted golden apple I struggled to much to obtain.
I return to my main base but the things there where fine, I reasoned they hadn’t been loaded breath a sigh of relief and continue to mourn my stuff, when suddenly I get a bright idea! In 1.8 you could still make enchanted golden apples! So I go to the launcher, open 1.8 aaand completely ignore the exact same warning I was given the previous day. Now everything in my main base was gone. Anything that wasn’t a placed block disappeared. I lost stacks or diamonds, gold and iron, all my villagers I painstakingly farmed (back in the day it was very tedious), a bloody nether star I hadn’t made into a beacon. My chicken farm, all my chests, item frames and armor stands, aaall gone.
I dropped the game for nearly a month until I went back and rebuild everything, learned how to backup my files and even did a few more projects here and there, until I finally tried multiplayer on the latest versions and drifted away from that world. And that’s the story.
Lesson learned, backup your worlds folks.