Murphy’s law: Whatever can go wrong, will.
In other words; when you come back home around lunch time, wondering what you can do during this unexpectedly sunny afternoon, if you decide to set up outside and paint the Ikea table you bought months ago, you can be absolutely certain that huge clouds will roll in when you get at exactly 50% of the table. You will hurry up, perhaps missing spots.
2 hours later, when you think you might be ok after all, no mistakes, clouds seem to be going, it will start raining, leaving you no choice but to bring indoors the toxic smelling nausea inducing table to let it dry until the next day.
Oh yeah, Murphy’s my very best pal.