Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

One of my stocks dropped 40% in 2 days, how should I mentally approach this?
You shouldn't be picking stocks in the first place. From New York Magazine, tweeted by Ezra Klein: New evidence for that reality comes from Goldman Sachs, via Bloomberg News. The investment bank analyzed the holdings of 854 funds with $2.1 trillion in equity positions. It found, first of all, that all those “sophisticated investors” would have been better off stashing their money in basic, hands-off index funds or mutual funds last year — both of them had higher average returns than hedge funds did. The average hedge fund returned 3 percent last year, versus 14 percent for the Standard & Poor’s 500.  Mutual funds do worse than index funds. Tangentially-related to the question of whether Wall Street types deserve their compensation packages is the yearly phenomenon in which actively managed mutual funds underperform the market. Between 2004 and 2008, 66.21% of domestic funds did worse than the S&P Composite 1500. In 2008, 64.23% underperformed. In other words, if you had a fund manager and his employees bringing their skill and knowledge to bear on your portfolio, you probably lost money as compared to the market as a whole. That's not to say you lost money in all cases. Just in most. The math is really simple on this one. Stock picking is fun, but undiversified and brings you competing with Wall Streeters with math Ph.Ds. and twenty-thousand-dollars-a-year Bloomberg terminals. What do you know about Apple's new iPhone that they don't? You should compare your emotional reaction to losing 40% in two days to your reaction to gaining 40% in two days...  then compare both of those to losing 6% and gaining 6%, respectively. Picking stocks is not financially wise. Period.