Karoshi: Death from being overworked.
Clint curses the fact that he is, still, undeniably human.
He's spent the entire week getting ready for his proposal to Natasha, and good god, what a tiring week it's been. Unfortunately, his status as an Avenger didn't help him in getting reservations at one of the best restaurants in the city. Fortunately, he wasn't above using the threat of the infamous Hulk smash to score a table for two within the same week. Bruce was rather dismayed when he found out, and he wanted to phone the managers to let them know that nothing of the sort would be going on, and Clint had disabled all the telephones in the tower until further notice.
He'd run around the city madly, setting up an enormous scavenger hunt throughout downtown, threatening, coercing, and pleading random civilians and store owners not to mess up any of the props for Natasha.
On Friday, when Natasha finally comes back from her mission in Sweden, Clint is tired to the bone and vibrating with nervous energy, the powder blue Tiffany's box burning a hole in his pocket. He hands Natasha the first clue and falls, trembling, onto the sofa, his hand over his eyes as he tries to catch a few hours of sleep before she finishes the quests and he has to leave for the restaurant.
He finds himself far too tense for any sort of relaxation, and so he does their laundry, finding solace in her cool silky underwear as he washes and dries and folds, breathing in the hot scent of pressed clothes as he irons and makes sharp creases in his shirts.
And when it does finally come time for him to leave, he finds his eyelids growing heavy as his clumsy fingers knot his tie, finds his tongue thick in his mouth as he gives directions to the cabbie to the restaurant.
She meets him there, and he barely has enough energy to get down on one knee, doesn't even finish the question as he opens the box, and the last thing he sees before he finally falls asleep is her smile and nod.