Endgame or Middlegame

Which part of chess to study, the opening, middlegame, or end-game. Some trainers have seen many good arguments about emphasizing end-game study, but to meet it seems logical (almost obvious) that the middle-game is the most important to study because in most chess games the endgame takes up the most time and neccesitates the largest amount of brute thought (at the level of play where you are at at least, for experts, class A players, masters etc this may not be as true and endgames could have their grater importance.) And of course, middlegame is strategy, tactics, position, sacrifices. Anyway you must be happy if you have improved your middlegame plays.