Offer your thoughts or opinion on the input financial query or topic using your financial background.

One of my stocks dropped 40% in 2 days, how should I mentally approach this?
Like @chirs, I'm of the opinion that you might want to buy more. I've done this a couple of times, price dropped a bunch, and I said, heck, I bought some last week, and this week I can get twice as much stock for about the same price. Brought down my average cost per share, and when the company was taken private, I actually didn't lose money - unlike some other people I know, who only bought at one price, watched the drop, and held on awaiting a recovery (which didn't happen in time before the big money swooped in on it). But to do this, you need to keep cash reserves (that, like @afforess says, you can afford to lose all of) on hand, awaiting buying opportunities.  This, too, is a cost - an opportunity cost.