This is a monthly chart that shows important relationships in terms of price and time. As we can see, through the 2008 crisis the market plunged almost 60% and saw around 350% increase thereafter, painting an all-time high in September 2018. Currently, the 10-year-cycle is seemingly done and another big selloff in the equity market appears to be zooming. The 25%, 33.33% and 50% areas from the all-time high are potential targets and reversal zones. Selling into strength seems reasonable here.