"Create in me a pure heart, O God, and renew a steadfast spirit within me." Psalm 51:10 NIV
Call out to God for a pure heart.
"How can a young man keep his way pure? By living according to your word. I seek you with all my heart; do not let me stray from your commands. I have hidden your word in my heart that I might not sin against you." Psalm 119:9-11 NIV
Seek God's ways. Remember (memorize) God's ways. Live inside the boundaries of God's ways.
"Above all else, guard your heart, for it is the wellspring of life." Proverbs 4:23 NIV
Guard what / who you love. Don't let false loves capture your heart.
"The good man brings good things out of the good stored up in his heart, and the evil man brings evil things out of the evil stored up in his heart. For out of the overflow of his heart his mouth speaks." Luke 6:45 NIV
Your conversations reflect what is going on in your heart.
"You were taught, with regard to your former way of life, to put off your old self, which is being corrupted by its deceitful desires; to be made new in the attitude of your minds; and to put on the new self, created to be like God in true righteousness and holiness." Ephesians 4:22-24 NIV
You can put on your new self... just like you can put your jacket on. It just takes practice.
"Be imitators of God, therefore, as dearly loved children and live a life of love, just as Christ loved us and gave himself up for us as a fragrant offering and sacrifice to God. But among you there must not be even a hint of sexual immorality, or of any kind of impurity, or of greed, because these are improper for God’s holy people." Ephesians 5:1-3 NIV
Imitate your Father.
Are there "hints" of impurity that your allow in your mind?
"Set your minds on things above, not on earthly things. For you died, and your life is now hidden with Christ in God." Colossians 3:2-3 NIV
This takes intentional focus.
"Let the word of Christ dwell in you richly as you teach and admonish one another with all wisdom, and as you sing psalms, hymns and spiritual songs with gratitude in your hearts to God. And whatever you do, whether in word or deed, do it all in the name of the Lord Jesus, giving thanks to God the Father through him." Colossians 3:16-17 NIV
Let God's Word live with you.
Do everything with thanksgiving.