Peace of soul comes to those with the right kind of anxiety about attaining perfect happiness, which is God. A soul has anxiety because it final and eternal state is not yet decided, it is still and always at the crossroads of life. This fundamental anxiety cannot be cured by a surrender to passions and instincts; the basic cause of our anxiety is a restlessness within time that comes because we are made for eternity.
If there were anywhere on earth a resting place other than God, we may be very sure that the human soul in its long history would have found it before this. ~ Archbishop Fulton J. Sheen