Feeling all virtuous for having cycled into work —10k uphill— only to realise that you forgot to pack a bra, your sports bra is soaked in sweat —from said 10k uphill— and you only have a tenner with you.
Cycling all the way back home at lunchtime to get a bra, having forgotten to press the record button on Strava.
Driving back to the office, fully clothed. Getting to your desk, looking at your docking station in puzzlement and then realising that you put your laptop in your cycling rucksack, which is at home 
Getting home, crafting a devastating PA reply to a snotty email from financial muppet, sending it with great satisfaction, only to then check your CC folder and see that your boss told you 5 minutes ago not to reply.
Pre-heating the oven, only to get to the stage of actually putting in the food and realising that you actually turned the knob for the grill and the oven is still stone-cold.
Putting the DC to bed, looking forward to sitting down with a new book and a Haagen Dazs, only to get to the freezer and realise that you already ate it.
Giving up on the day, going upstairs to brush your teeth to find that DD has left the toothpaste cap off again and it’s gone hard around the hole.
Getting to bed, to find it stripped.
Making the bed, sinking thankfully into its warm softness, closing your eyes... then DD starts crying.
Worst day ever.