We live in a world that often promotes and celebrates things that are contrary to God's principles. But even though we live in the world, we're not of the world (John 17:16), and as long as you have a rich store of God's Word in your heart, you'll be able to filter all the information coming to you, capture every negative thought, and make it obey Christ (2 Corinthians 10:5).
You can achieve this by meditating on God's Word. One of the ways to meditate is to mutter the word, that is speak it under your breath to yourself. When you do this, you’ll talk your spirit up and drown out negative voices and thoughts. I learnt to do this as a teenager: I'd lock myself in my dad's car in the garage, just to be alone so I could meditate. This is something you need to do often. Learn to lock yourself away in a private place to meditate without disturbing others. There you can mutter God's Word to yourself until it takes root in your spirit, and becomes personal to you. Then you shout it until you completely drown every negative voice or thought of fear, unbelief, or failure.
As you do this, the Word will gain the mastery over your mind, and you, in turn, will have the mastery over life's circumstances.
Prayer
Dear Father, I thank you for showing me how to meditate on your Word and have it richly stored up in my spirit. Your Word fills my mind with thoughts that are consistent with my identity in Christ today, in Jesus' Name. Amen.