8 Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.
2 Corinthians 10:4-6
4 For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;
5 Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;
6 And having in a readiness to revenge all disobedience, when your obedience is fulfilled.
Just two of many scripture dealing with thoughts and the mind. Just as Alikat has posted too:
2 Timothy 1:6-7
6 Wherefore I put thee in remembrance that thou stir up the gift of God, which is in thee by the putting on of my hands.
7 For God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.
God wants us to succeed, and has given us the strength and power to do so through His son Jesus Christ. I have meditated on these scriptures in my times of need in the past and they have boosted my confidence in having power over my mind and my thoughts. We are victorious in Christ. satan has no power over us, Jesus Christ has already defeated him. satan still likes to try to tempt us and make us fail, but the good news is that we don't have to let him!