How to guard your heart

The Lord is near the brokenhearted, who call on Him in truth (raw honesty)
"The Lord is near to those who have a broken heart, and saves such as have a contrite spirit." Psalm 34:18. "The Lord is near to all who call upon Him, To all who call upon Him in truth." Psalm 145:18

Let God have your heart
"Give me your heart" Proverbs 23:26. "I, the Lord, search the heart, I test the mind, even to give every man according to his ways, according to the fruit of his doings." Jeremiah 17:10. "I will give you a new heart and put a new spirit within you; I will take the heart of stone out of your flesh and give you a heart of flesh. I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them." Ezekiel 36:26-27.

Let God search your heart, He knows it better than you do
“Search me, O God, and know my heart: try me, and know my anxieties: and see if there be any wicked way in me, and lead me in the way everlasting.” Psalm 139:23-24. "For as [a man] thinks in his heart, so is he." Proverbs 23:7.

"Who can understand his errors? Cleanse me from secret faults. " Psalm 19:12. "Teach me, and I will hold my tongue; cause me to understand wherein I have erred." Job 6:24.

"The heart is deceitful above all things, and desperately wicked; Who can know it?" Jeremiah 17:9. "...God is greater than our heart, and knows all things." 1 John 3:20b. "O Lord, You have searched me and known me. You know my sitting down and my rising up; You understand my thought afar off." Psalm 139:1-2..

Pray for a new heart
“Create in me a clean heart, O God, and renew a steadfast spirit within me. Do not cast me away from Your presence, and do not take Your Holy Spirit from me.” Psalm 51:10-11.

Abide in God's word and you'll be freed from the lies that lead to sin
"Let your heart retain my words" Proverbs 4:4a. "For the word of God is living and powerful.. and is a discerner of the thoughts and intents of the heart." Hebrews 4:12. “If you abide in My word, you are My disciples indeed. and you shall know the truth, and the truth shall make you free.” John 8:31-32.

"Your word I have hidden in my heart, That I might not sin against You." Psalm 119:11. "Your words were found, and I ate them, and Your word was to me the joy and rejoicing of my heart; For I am called by Your name, O Lord God of hosts." Jeremiah 15:16. "I delight to do Your will, O my God, And Your law is within my heart." Psalm 40:8.

Careful what you say or think (it begins in the heart)
"[Guard] your heart with all diligence, For out of it spring the issues of life." Proverbs 4:23. "A good man out of the good treasure of his heart brings forth good; and an evil man out of the evil treasure of his heart brings forth evil. For out of the abundance of the heart his mouth speaks." Luke 6:45.

"Let the words of my mouth and the meditation of my heart be acceptable in Your sight, O Lord, my strength and my Redeemer." Psalm 19:14. "Set a guard, O Lord, over my mouth; Keep watch over the door of my lips." Psalm 141:3. "Death and life are in the power of the tongue, and those who love it will eat its fruit." Proverbs 18:21. "A wholesome tongue is a tree of life, But perverseness in it breaks the spirit." Proverbs 15:4. "Keep your tongue from evil, and your lips from speaking deceit. Depart from evil and do good; Seek peace and pursue it." Psalms 34:13-14.

"Whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy—meditate on these things." Philippians 4:8. "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" 2 Corinthians 10:5

Don't let anything "choke" the God's word out of your heart
Matthew 13:22 Now he who received seed among the thorns is he who hears the word, and the cares of this world and the deceitfulness of riches choke the word, and he becomes unfruitful.

Let Christ and His word dwell in your heart
"For this reason I bow my knees to the Father of our Lord Jesus Christ, from whom the whole family in heaven and earth is named, that He would grant you, according to the riches of His glory, to be strengthened with might through His Spirit in the inner man, that Christ may dwell in your hearts through faith; that you, being rooted and grounded in love, may be able to comprehend with all the saints what is the width and length and depth and height—  to know the love of Christ which passes knowledge; that you may be filled with all the fullness of God." Ephesians 3:14-19

Colossians 3:16 Let the word of Christ dwell in you richly in all wisdom, teaching and admonishing one another in psalms and hymns and spiritual songs, singing with grace in your hearts to the Lord.

Let God strengthen your heart and pour His love into it
"Be of good courage, And He shall strengthen your heart, All you who hope in the Lord." Psalm 31:24. "Now hope does not disappoint, because the love of God has been poured out in our hearts by the Holy Spirit who was given to us." Romans 5:5.

Make a melody in your heart
"See then that you walk circumspectly, not as fools but as wise, redeeming the time, because the days are evil. Therefore do not be unwise, but understand what the will of the Lord is. And do not be drunk with wine, in which is dissipation; but be filled with the Spirit, speaking to one another in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord, giving thanks always for all things to God the Father in the name of our Lord Jesus Christ, submitting to one another in the fear of God." Ephesians 5:15-21