Justification is an act of God, whereby He declares a sinner to be righteous because of that sinner’s faith in Christ.

Romans 5:8-9 (ESV)
… but God shows his love for us in that while we were still sinners, Christ died for us. 9 Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God.

Justification does not make anyone holy; it simply declares him to be not guilty before God, and therefore treated as holy.

2 Corinthians 5:21
For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God.

Sanctification refers to the process of being made holy, and centers on the heart, mind, and behavior of the Christian.

Romans 6:15-23
What then? Are we to sin because we are not under law but under grace? By no means! 16 Do you not know that if you present yourselves to anyone as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness? 17 But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed, 18 and, having been set free from sin, have become slaves of righteousness. 19 I am speaking in human terms, because of your natural limitations. For just as you once presented your members as slaves to impurity and to lawlessness leading to more lawlessness, so now present your members as slaves to righteousness leading to sanctification. 20 For when you were slaves of sin, you were free in regard to righteousness. 21 But what fruit were you getting at that time from the things of which you are now ashamed? For the end of those things is death. 22 But now that you have been set free from sin and have become slaves of God, the fruit you get leads to sanctification and its end, eternal life. 23 For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.

Why do I still struggle with sin?

1 John 1:8
If we say we have no sin, we deceive ourselves, and the truth is not in us.

Romans 7:15
For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate.

Romans 7: 21-23
So I find it to be a law that when I want to do right, evil lies close at hand. 22 For I delight in the law of God, in my inner being, 23 but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members.

There are 3 forces at work as we fight against sin: The Flesh, Our Redeemed Spirit, and Our Will

Paul mentions 2 tactics that we should employ, if we want to defeat sin in our lives.
1. Consider ourselves dead to sin
2. Present ourselves to God

Romans 6:11-13
So you also must consider yourselves dead to sin and alive to God in Christ Jesus. 12 Let not sin therefore reign in your mortal body, to make you obey its passions. 13 Do not present your members to sin as instruments for unrighteousness but present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness.

One of the reasons that we do not aggressively confront sin in our lives is that we have become comfortable with sin.

We must wake up to the realization that sin is an apex predator, and it will wreak havoc in your life, if left unchecked.

Genesis 4:7-8 (NIV)
“If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you…”

Romans 7:24
Wretched man that I am! Who will deliver me from this body of death?

Romans 7:25
Thanks be to God through Jesus Christ our Lord!

We are taught in Scripture that, to deal with our sin, we must confess and repent.

Proverbs 28:13 (NLT)
People who conceal their sins will not prosper, but if they confess and turn from them, they will receive mercy.

Confession of sin is the admission of what we did, and the agreement with God that our actions or words were wrong.

Repentance is an inner change of mind, resulting in an outward turning around, to face and to move in a completely new direction.