Why do we train in this technique? This is a method of purification. Just as the dishes have to be washed before we eat, the mind has to be trained in this way before it can abide in tranquility. Special techniques are needed to tame the mind; without these special techniques, the mind cannot be tamed. To control the mind, we must have a way, otherwise the more we try to control it, the less likely we are to succeed; just like the more you try to put something out of your mind, the harder it is to forget. As with all things in general, if we have methods, we can deal with problems easily; if we do not have methods, we will not succeed even with effort. This is also the case with practice.
~Depicted from THE FOUR SEALS OF DHARMA - Preparing for the Preliminaries