The current "cannot sleep" message feels too robotic, and i think it would be cool if there were possibly a config to either change that ourselves or have pre-made, more "natural" messages.
Something as simple as "You cannot sleep during a blood moon"
Or maybe even more flavorful: "All the monsters around make it hard for you to sleep."
Maybe even just: "You can't sleep right now . . . Good Luck . . . "

You can change this via a lang file with a resource pack

This would be the key: https://github.com/CorgiTaco/Enhanced-Celestials/blob/Forge-1.16.X/src/main/resources/assets/enhancedcelestials/lang/en_us.json#L26