In our view, though, investment students need only two well-taught courses-How to Value a Business, and How to Think about Market Prices. Your goal as an investor should simply be to purchase, at a rational price, a part interest in an easily-understandable business who's earnings are virtually certain to be materially higher five, ten and twenty years from now.
Warren BuffettYou should be unconcerned about short-term price action when you own the securities directly, just as you were unconcerned when you owned them indirectly through BPL. I think about them as businesses, not "stocks", and if the business does all right over the long term, so will the stock.
Warren Buffett