Compass Bearing

I have looked at every post involving the compass bearing and the use of the "inside" of the rose...I cant see, to grasp why there is not a compass that is not relative to the ship but true (actual)...In the heat of the battle when I enter a course change on the compass it is always 180 degrees off, as it is not True, absolute but relative...What am I missing .?? North is north, isnt it...??