"Markets can remain irrational longer than you can remain solvent." John Maynard Keynes
It's generally dangerous to short such an irrational market but SPY presented a low risk entry today with this potential double-top. She is running out of momentum so I expect a retracement at the very least, if not a full reversal. There are many other signs that show she may be topping out (divergence with stocks >200MA relative to index highs, advance/decline line relative to index are just 2 examples).