"Fixing one's thoughts" takes diligent effort. I can't be naive about the graphic evil and filth of this world, but I'm also not asked to ruminate in that shadowy place. We have this Scripture so we know God knows we can't survive in a constant state of "saving the world". He hasn't required that of us. He knows if we internalize the images of grief, injustice and carnality we are hit with every moment we live in this world it's only a matter of time before we self-destruct. I have been given permission to live in heaven now, it is not demanded of me that I undergo some self-absorbed mental/spiritual initiation. Jesus Christ already went to hell and back. He does not ask me to go to hell and live there, so that I can somehow become strong enough as to be as invincible as He is. He is the only one who could have entered darkness and shadow and lived through it all. We think we have personal tabs on the depths of evil. We are cocky to run ahead so rashly. Our pride is only fuel for hell's sulfuric fire.
What I am asked for is humility enough to hide myself in Him, to realize the evil but not to be sidelined. To be invincible because I have been given the privilege of living in heaven right now, and there are no precursors other than simply knowing Christ. The more I know Him, the more of His purity, honor and loveliness abide within me for my access. Then, the paralysis (like chloroform) the enemy holds over our senses is knocked off. When we can see heaven, we can see the actions of God. We are not defeated any longer because we have given up replaying and planning our own heroic attack on the bowels of hell. This practice is useless because we know we will not be successful, for what human power can stand? In human strength we see ourselves rendered helpless even in the best blustering daydream we can muster.
In the "precious lifeblood" (1 Peter 1:19) of the Lamb we have the power to suffer earth because we're living in heaven. As we live in heaven, the Holy Spirit will impact earth through us. The actions we are to take on the behalf of those God is calling will be clear. We will not be overtaken by evil but we will respond, alive and well, with good. The trust of simple children, so grateful that Daddy does the dirty work, will release the power of heaven to devastate and regenerate the slimiest pit imaginable.
"And now, dear brothers and sisters, let me say one more thing as I close this letter. Fix your thoughts on what is true and honorable and right. Think about things that are pure and lovely and admirable. Think about things that are excellent and worthy of praise. Keep putting into practice all you learned from me and saw me doing, and the God of peace will be with you." Philippians 4:8