I have a very high strung, nervous temperament about most things, but not about investing. I can't afford that luxury.
In addition I am sure it helps a lot that I have several different income streams that are independent of market conditions. As my dear departed mother would have said if in similar circumstances, rolling her eyes, "This wasn't by accident, you know!"
Still, over 50% of my spending money DOES come from my portfolio, so I keep an eye on it. To be honest, this just seems like nothing after going through 2008-2009. On March 9th, 2009, the Dow Jones hit 6443; yesterday it hit 16014. The market could become just as bad as it's 2009 low, or worse! I'm not saying that it won't because I have no idea. But it's not there, and for me this dip is just so insignificant thus far.
I came out of 2008-2009 with a somewhat larger portfolio than previously because I bought low instead of selling. This time, if the market plunges just as far, I won't have as much cash to spend buying low. Still, I think I would be just fine as long as I don't sell.