From the Oracle of Omaha, seems to explain the mood swings here pretty well.
http://www.berkshirehathaway.com/letters/1987.html
Quote:Ben Graham, my friend and teacher, long ago described the mental attitude toward market fluctuations that I believe to be most conducive to investment success. He said that you should imagine market quotations as coming from a remarkably accommodating fellow named Mr. Market who is your partner in a private business. Without fail, Mr. Market appears daily and names a price at which he will either buy your interest or sell you his.
Even though the business that the two of you own may have economic characteristics that are stable, Mr. Market's quotations will be anything but. For, sad to say, the poor fellow has incurable emotional problems. At times he feels euphoric and can see only the favorable factors affecting the business. When in that mood, he names a very high buy-sell price because he fears that you will snap up his interest and rob him of imminent gains. At other times he is depressed and can see nothing but trouble ahead for both the business and the world. On these occasions he will name a very low price, since he is terrified that you will unload your interest on him.
Mr. Market has another endearing characteristic: He doesn't mind being ignored. If his quotation is uninteresting to you today, he will be back with a new one tomorrow. Transactions are strictly at your option. Under these conditions, the more manic-depressive his behavior, the better for you.
But, like Cinderella at the ball, you must heed one warning or everything will turn into pumpkins and mice: Mr. Market is there to serve you, not to guide you. It is his pocketbook, not his wisdom, that you will find useful. If he shows up some day in a particularly foolish mood, you are free to either ignore him or to take advantage of him, but it will be disastrous if you fall under his influence. Indeed, if you aren't certain that you understand and can value your business far better than Mr. Market, you don't belong in the game. As they say in poker, "If you've been in the game 30 minutes and you don't know who the patsy is, you're the patsy."
- Warren BuffettQuote:Following Ben's teachings, Charlie and I let our marketable equities tell us by their operating results - not by their daily, or even yearly, price quotations - whether our investments are successful. The market may ignore business success for a while, but eventually will confirm it. As Ben said: "In the short run, the market is a voting machine but in the long run it is a weighing machine." The speed at which a business's success is recognized, furthermore, is not that important as long as the company's intrinsic value is increasing at a satisfactory rate. In fact, delayed recognition can be an advantage: It may give us the chance to buy more of a good thing at a bargain price.
Sometimes, of course, the market may judge a business to be more valuable than the underlying facts would indicate it is. In such a case, we will sell our holdings. Sometimes, also, we will sell a security that is fairly valued or even undervalued because we require funds for a still more undervalued investment or one we believe we understand better.
We need to emphasize, however, that we do not sell holdings just because they have appreciated or because we have held them for a long time. (Of Wall Street maxims the most foolish may be "You can't go broke taking a profit." ) We are quite content to hold any security indefinitely, so long as the prospective return on equity capital of the underlying business is satisfactory, management is competent and honest, and the market does not overvalue the business.
http://www.berkshirehathaway.com/letters/1987.html
