I dollar cost average so my answer is:
Nothing. I invest on the 10th of every month.
Except I did do this:
Even my silver ETF dropped - that spoiled my diversfication theory by owning a commodity.
That should have stayed put or gone up. Coulda, woulda, shoulda.
Shows you what I know, LOL.
Well on the bright side, Silver was up 10% since last month, and now back down 5%. What are you going to do - it was the only part of my portfolio that gained enough so the loss was less than the gain.