At the moment of salvation we are sanctified - set apart/made holy in standing before God positionally in Christ. 1 Corinthians 6:11 - Such were some of you; but you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus Christ and in the Spirit of our God. Acts 26:18 - to open their eyes, in order to turn them from darkness to light, and from the power of Satan to God, that they may receive forgiveness of sins and an inheritance among those who are sanctified by faith in Me.
Yet we also see progressive sanctification in which the reality of that holiness becomes more and more evident in our actions, words, thoughts, attitudes, and motives. 1 Thessalonians 4:3-4, we read - For this is the will of God, your sanctification: that you should abstain from sexual immorality; that each of you should know how to possess his own vessel in sanctification and honor.
So becoming washed, sanctified and justified in Christ is a one time event and is not a process, yet abstaining from sexual immorality is not a one time event, but an ongoing process. Here is how I understand it. The believer possess a positional, judicial standing of righteousness in Christ and, second, an ongoing process of growth in practical, progressive holiness which becomes increasingly evident in our actions, words, thoughts, attitudes, and motives.