The happiness of those who want to be popular depends on others; the happiness of those who seek pleasure fluctuates with moods outside their control; but the happiness of the wise grows out of their own free acts. 
- Marcus Aurelius

The true investor is scarcely ever forced to sell his shares, and all other times he is free to disregard the current price quotation. He need pay attention to it and act upon it only to the extent that suits his book, and no more. Thus the investor who permits himself to be stampeded or unduly worried by unjustified market declines in his holdings is pervesely transforming his basic advantage into a basic disadvantage. That man would be better off if his stocks had no quotation at all, for he would then be spared the mental anguish caused him by other persons' mistakes of judgement.

- Benjamin Graham