Some of the old wall st sayings have a bit of merit, i think they are derived from old warhorse stock traders who have learnt the hard way through either lost money or long careers.
My personal faves are.

• A rising tide lifts all boats
• The trend is your friend until the end
• Bulls make money , bears make money and pigs get slaughtered.
  The longer i stay in this game the more they seem to make sense :) .