The most obvious thing we can do is to draw certain key portions of Scripture into our minds and make them a part of the permanent fixtures of our thought. This the primary discipline of the thought life. We need to know the like the back of our hand, and a good way to do that is to memorise them and constantly turn them over in our minds as we go through the events and circumstances of our life.
The desired effect will not be realised by focusing on isolated verses, but will certainly come as we ingest passages, such as Romans 5:1-8 and 8:1-15, 1 Corinthians 13 or 3:1-17. When you take these into your mind, your mind will become filled with the light of God himself. And light shines in the darkness and darkness looses. When the light comes into a room, we do not have to say “Now what are we going to do about the darkness?” Its gone!
From the book "Renovation of the Heart: Putting on the Character of Christ (Th1nk LifeChange)"