This may seem to be a long word, but it is vital to every Christian. Sanctification is that process which God uses to make the believer more like the Lord Jesus Christ. That is what the Holy Spirit is doing all of the time. The Apostle Peter writes:
Chosen according to the foreknowledge of God the Father, through the sanctifying work of the Spirit, to be obedient to Jesus Christ and sprinkled with his blood. 1 Peter 1:2 NIV
This is not some optional extra just for keen Christians – it is for every Christian.
There are some people who think that sanctification is all about what they do for God – but notice what Peter writes – it is the sanctifying work of the Spirit. In fact, what is going on is that the Holy Spirit is the one who prompts the believer to do good works as a response to what Christ has already done.
As Christians, we need to ask God that by His Spirit, he will continue that sanctifying work in our lives so that we will have the desire to please him. Paradoxically, as we do so, we will more and more realise how far short we fall of his perfection. But He continues His good work in us and we know that one day when we see him we will be completely perfect. That will be sanctification completed!