Changing a mindset takes time... and it takes renewing your mind to the Word of God. Replace your negative thoughts and those that keep you in bondage with God's Word on a DAILY basis. Sometimes you need to do it several times a day until HIS thoughts now become YOUR thoughts. You can do it. PERSEVERE!
"We are destroying speculations and every lofty thing raised up against the knowledge of God, and we are taking every thought captive to the obedience of Christ..." 2 Cor. 10:5