When people say “I want to lose weight” what they generally mean is “I want to lose fat”. While hundreds of variables influence scale weight, fat loss is limited to a handful of physiological processes, none of which operate on a standard 24 per day time clock that humanity organizationally favors.
As a result, day to day fluctuations are almost entirely irrelevant. 30 day trend lines are about the smallest time frame to seriously consider for data validity purposes.
What time do you weigh yourself? I try for right after my morning bathroom trip, and before I’ve had anything to eat or drink. But I figure that my true weight is an average of my numbers for the whole week., so one day of my weight seeming off doesn’t bug me too much.