We got lots of things going on here. One is that market crashes happen --the record shows that in the 1930's 7/8 of the value of U.S. businesses was destroyed. Another is that for hundreds of years America's been a tremendous wealth creating force for good--
--and those who acted like America was an empty balloon ended up wishing they hadn't. The crash in the '30's seemed big at the time but it was erased in less than a decade.
Finally, while none of us know what's happening tomorrow, most of us put our money on being ahead ten years from now. Others buy into the kind of crash that happens once very 20 years or so, and the rest say the bubble's going to pop but they know better than to actually put their money on the idea.