Tonight, I found myself getting bored and moderately fatigued while loading some .44 Mag, after prepping a bunch of brass.
My solution: I poured the powder back in its container, wrote down what I was doing and that the next charge increment was due (load data was already recorded), covered the press and scale, and walked away for the night.
There are quite a few brass prep, sizing, or expanding tasks I'll perform while tired/fatigued (if needed), but I don't mess with powder. If I have to call it quits, I come to a good stopping point and walk away. I don't try putting things away and moving to a less critical task. I just take care of any open powder or primers, and leave everything right where it's at.
"Such is the strange way that man works -- first he virtually destroys a species and then does everything in his power to restore it."