Concentration is taught by the mystics in order to exercise the will, making it capable of using all the faculties. A person with will power can remember what he wishes to remember and can forget what he wishes to forget. All things which deprive one of one's freedom in life are undesirable. The mind must be free from all bad impressions of life, which take away one's rest and peace. By concentration one is able to hold a certain thought one desires and to keep away all other thoughts, and when one is able to keep away all the thoughts one does not want to think about, it becomes easier to throw away the impressions of years, if one wishes to forget them. Bad impressions, however old and intimate, are like rubbish accumulated, which should be removed in order to make the house clean. The human heart is the home of the soul, and upon this home the comfort and peace of the soul depend.