If the unemployment rate wasn't at an all time low, I would worry. One thing that concerns me is the amount of consumer debt we have right now. It's dominoes right... people take there money out of the market for three reasons (that I know of)...
1. They need the money
2. Fear and Panic
3. RMD
I only worry about #1 and #2, and usually 1 is the driver of 2 even if uncorrelated. FOMO, or 'everyone is doing it mentality'. I almost don't even fear #2, because eventually those folks realize they are ACTUALLY missing out by being OUT of the market. Eventually if you pulled the money for fear and panic, you would look around and say, okay where else can I beat inflation...and back in goes the dough.
Okay maybe there is a #4, death.