Stefan Klein im Interview: "Der innere Schweinehund ist ein irrer Mythos"

In other words, the faster you try to change, the more likely you are to backslide. The very pursuit of rapid change dials up a wide range of counteracting forces which are fighting to pull you back into your previous lifestyle. You might be able to beat equilibrium for a little while, but pretty soon your energy fades and the backsliding begins.