I wanted to get something from the airing cupboard - simple, you'd think.
Stupidly I decided not to disturb Himself, who was working out in the garden. 'All' I needed to do was take the little stepstool upstairs to reach the shelf. I carried it to the bottom of the stairs - no problem, then lifted it, stair by stair; pop the stool down, climb a step, lift and repeat. by the time I got to the top of the stairs I was drenched with sweat, and I was shaking so much I couldn't even operate the heart rate monitor until after I'd been flumped on the bed for several minutes.
All the careful resting and gentle pacing I've done over the past few weeks, all wrecked in 5 minutes of my own utter stupidity.