You have to learn not to get too caught up in day to day price fluctuations, it'll give you ulcers. Today's price drop was interesting, but not shocking. It's just back to where it was a week ago. You're either willing to take a position at this price level or you're not. Do your due diligence, evaluate the company/stock and make up your mind. Do you think that Warren Buffett is worried that Apple has dropped 30% from its high? Probably not. He probably sleeps just fine. (I own some AAPL too) If owning stocks is gonna keep you up at night every time they drop you should probably stick with a nice safe mutual fund.
Otherwise trust your research, know what you're buying and why, and have a plan. I know it can be frightening, but so long as you don't overextend yourself, you'll get used to it. As they say, this too shall pass.