As you can see in the left screenshot below, Chef Elaine's Apple Watch was very low on memory (only 0.3 GB remaining) and over half of the total storage was being used by "Other", whatever that means. Most of that "Other" was reclaimed by a simple restart of the watch, freeing up 2.4 GB seen in the after-boot picture on the right. There is still another 2-3 GB of "Other" remaining, but that would require totally resetting and restoring the watch and that's not worth the effort.
It used to be that remembering to wind your watch was the only thing to worry about. Miss those simpler days.