Idolatry inflates something to function as a substitute for God

For where your treasure is, there your heart will be also. Matthew 6:21, Luke 12:34 (NIV)

An idol is something within creation that is inflated to function as a substitute for God. It may be an object, a person, an activity, a sport, a role you play, an institution or organization, an idea, a pleasure, a hero, your family, your work, even your work for the Lord – anything that can become a substitute for God. It does not have to be a full-sized replacement for God; it may be only a part of your life. Idolatry is not necessarily a denial of God or His existence. An idol may even be made out of something that is a good thing in its own right. As soon as loyalty to anything or anyone leads us to disobey God, we are in danger of making it an idol. (See Exodus 20:4; Colossians 3:5.) - BsfInternational.org

Starts within our heart, what you treasure

• For from within the hearts of men come evil thoughts, sexual immorality, theft, murder, adultery, Mark 7:21
• For where your treasure is, there your heart will be also. Matthew 6:21, Luke 12:34

We give our heart and life to God and he makes us righteous

• Do not present the parts of your body to sin as instruments of wickedness, but present yourselves to God as those who have been brought from death to life; and present the parts of your body to Him as instruments of righteousness. Romans 6:13
• For if you live according to the flesh, you will die; but if by the Spirit you put to death the deeds of the body, you will live. Romans 8:13

Our new nature convicts us to repent from sin that was once natural for us

• Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral, nor idolaters, nor adulterers, nor men who submit to or perform homosexual acts, 1 Corinthians 6:9
• And that is what some of you were. But you were washed, you were sanctified, you were justified, in the name of the Lord Jesus Christ and by the Spirit of our God. 1 Corinthians 6:11
• Flee from sexual immorality. Every other sin a man can commit is outside his body, but he who sins sexually sins against his own body. 1 Corinthians 6:18

Our desires change and we long for purity, living impure lives brings shame and guilt

• I am afraid that when I come again, my God will humble me before you, and I will be grieved over many who have sinned earlier and have not repented of their acts of impurity, sexual immorality, and debauchery. 2 Corinthians 12:21
• The acts of the flesh are obvious: sexual immorality, impurity, and debauchery; Galatians 5:19
• Having lost all sense of shame, they have given themselves over to sensuality for the practice of every kind of impurity, with a craving for more. Ephesians 4:19

Only Jesus can change our heart, removing the sin

• But among you, as is proper among the saints, there must not be even a hint of sexual immorality, or of any kind of impurity, or of greed. Ephesians 5:3
• For of this you can be sure: No immoral, impure, or greedy person (that is, an idolater), has any inheritance in the kingdom of Christ and of God. Ephesians 5:5
• In Him you were also circumcised in the putting off of your sinful nature, with the circumcision performed by Christ and not by human hands. Colossians 2:11

God is pure treasure, relationship with him satisfies completely

• For the love of money is the root of all kinds of evil. By craving it, some have wandered away from the faith and pierced themselves with many sorrows. 1 Timothy 6:10
• Keep your lives free from the love of money and be content with what you have, for God has said: "Never will I leave you, never will I forsake you." Hebrews 13:5