To See God, the Soul Must Be Purified
10 Wherefore, since it is our duty fully to enjoy the truth which lives unchangeably, and since the triune God takes counsel in this truth for the things which He has made, the soul must be purified that it may have power to perceive that light, and to rest in it when it is perceived. And let us look upon this purification as a kind of journey or voyage to our native land. For it is not by change of place that we can come nearer to Him who is in every place, but by the cultivation of pure desires and virtuous habits.
Source: Christian Doctrine (New Advent)