It can be difficult in our humanity to rid ourselves of the clutter in our thoughts. Circumstances and situations can evoke emotions within us that can be difficult to cope with and lead to unholy thought processes.
It takes an active, conscious effort to partner with God in the valleys...to bring every thought captive to the obedience of Him...to think, practice and dwell on truth and that which is holy and pleasing unto God.
But, when we make the Godly choice...when we are obedient...He is faithful to bless us with His enduring peace...as we think on these things.
Finally, brethren, whatever is true, whatever is honorable, whatever is right, whatever is pure, whatever is lovely, whatever is of good repute, if there is any excellence and if anything worthy of praise, dwell on these things. The things you have learned and received and heard and seen in me, practice these things, and the God of peace will be with you.
2 Corinthians 10:4-5
For the weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God, bringing every thought into captivity to the obedience of Christ...
For whoever serves Christ in this way is pleasing to God and approved by men.
And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus.