You were building for hours and you haven’t noticed the time that passed!
That’s why!
Unfortunately on our console we have a ram issue with this game, so you’re not only loosing your day progress but the game deletes feat progress that’s no way (that i am aware of) to restore in the particular character.
I explain my experience here…
The current performance of PlayStation 5. Friendly conversation and feedback, no rant - #17 by stelagel
So the only workaround i have to give you is play with a maximum 2h timer, then log out really slowly, close the game correctly, and restart your console to continue playing!
Give time to your machine ram to pass the info to your hard drive correctly, or doom unfortunately 
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I am really sorry my dearest exile you had to go through this and thanks a million for reporting your issue!
It’s really lovely to have you around.
Ps. Play as you wish, gaming should be “happy hour”. Feel no remorse about how you enjoy to play a game, you do nothing wrong. The master builders of this game build mostly on creative mode.
If it wasn’t “creative” it wouldn’t had this name. So feel free to be creative and have fun 
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