I'm guessing more money has been lost over the years by trying to grab the top or bottom tick of a move then any other trading aspiration.
The expectation is for another 450 S&P points down. Another expectation is watching from the sidelines of the first 10% of that move, which is where the market may be currently. A close this week below 831.32 creates the first red bar of what should be a tsunami of red bars on the above Weekly S&P chart.
Expect a head fake, or two, or ten, before the real decline begins......