Silly things that shouldn't be repeated:

Like today : Storing a pre-made (and used) gun-blue liquid stain in a glass jar.
Placing jar on high shelf.
Above the milling machine.
Sat on steel-clad bench.
Slamming the shed door as I leave the shed, hearing something fall off a shelf and thinking "I'll sort that later".

Result: One massively stained steel bench top and a camo-patterned bed on the mill. And glass and liquid everywhere.

Lesson learnt: Don't store liquids on high shelves.