Okay.
Having taken some time away, done some deep breathing, and, finally, largely recovered from the shock of the twenty-pound butter dish, I've mustered the strength to come back and share my Thing Which Should Be A Piece Of Cake But Is Inexplicably Rock-Bloody-Hard:
Pantyliner positioning.
(Or sanitary towel, but I'm very light so all I need to use is a pantyliner, and only for a couple of days.)
I'm in my late thirties, I've been doing this, on and off, since I was 11, so I have over a quarter of a century of experience at what amounts to correctly placing a big sticker on a strip of fabric.
Yet somehow, a not-insignificant percentage of the time, after carefully placing and smoothing down the pantyliner, I pull up my kecks and the damn thing is 2cm too far forward, or an equal distance too far back.
How have I not got this thing 100% down by now?! I guarantee that by the time I've cracked it I'll have hit the menopause.