If you’re young (or old but have expendable money) you should be buying.
As a person that is young (compared to.. I don't know Jerry Seinfeld) who has lots of years ahead (hopefully) I am taking this chance to put money into this market, because I have the flexibility to make more money in the future if it all goes to shit.
I'm betting that it won't, and I'm also betting that I will be a much happier person for doing so. Maybe not tomorrow, maybe not next week, maybe not in the near future. But compared to stuffing my extra money away into "safer" investments and slowly building my nest egg now when I am young I find it to be a better albeit much riskier alternative.
I take solace in the fact that the money that I've invested can disappear tomorrow and I won't be out of my home, or car or go hungry, because I've only put in what I can afford to lose. So if I can offer some unsolicited advice to the younger generation here (and the older generation that has trouble controlling impulses) it is this:
Don't fucking invest more than you are willing to lose, use your common sense with investing, be better than the primitive impulses inside you want you to be. It won't make you happy to see paper losses (as long as you keep them on paper) but it will give you the confidence to ride out the storm.
Good luck, and be smart.