This Too Shall Pass
I love this adage. Having read the Wikipedia article on it (you have to like any sentence that has its own Wikipedia article) I seem to be in good company; there's wise men, various royals and Abe Lincoln.
One of my plans for if/when I have stupid amounts of money to throw at frivolous projects: write this somewhere that the passing will take a while.
I can probably afford to get it carved in a lump of granite now. Wandering round a graveyard gives you an idea of how long that'll take to pass. I put it at a couple of centuries (if you can stop future people finding a better use for the chunk of granite for that long).
I like the idea of making a standing stones version of the phrase. Stone henge, and the other stone circles, suggest that these can last a few millenia. Though we don't really know how many didn't survive...
Next step up would be to reshape a mountain to spell it out. Mt Rushmore style. A quick Google puts the cost of that on the order of $10 billion. A bit out of my price range at the moment. But about pocket change for a decent sized government. Anybody contemplating a bank bailout or a couple of aircraft carriers: how about carving a mountain to say "This too shall pass" instead?
Properly into mad billionaire territory (I'm looking at you Elon Musk) we could write it on the moon. I could take a swing at figuring out what that would take and how long it would last but this seems like the kind of problem that can be outsourced to xkcd/what if. I have submitted it so I guess we'll see if Randall's productivity is sufficiently superior to mine that he gets to a random submission before I get round to looking into something I've actually wondered about.