For this to come about you must repeatedly retreat into your heart and remain there, keeping yourself free from everything, so far as is possible. You must always keep the eye of your mind clear and still. You must guard your understanding from daydreams and thoughts of earthly things. You must completely free the inclination of your will from worldly cares and cling with all your being to the supreme true good with fervent love. … More On Purity of Heart, Which is to be Sought Above All Things