Ephesians 2:10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.
Philippians 2:13 For it is God which worketh in you both to will and to do of his good pleasure.
"As with all the items that this chapter discusses, sanctification is a work of God; however, it is SYNERGISTIC in nature, meaning that it is also in a sense a work of man, and involves his conscious decision and effort in the process. As Paul writes:
Therefore, my dear friends, as you have always obeyed – not only in my presence, but now much more in my absence – continue to work out your salvation with fear and trembling, for it is God who works in you to will and to act according to his good purpose. (Philippians 2:12-13)
The Christian is to actively take his part in sanctification, and deliberately pursue a life of obedience to God "in fear and trembling." Nevertheless, the passage explains that even the working out of our salvation is in fact a work of God: "It is God who works in you to will and to act according to his good purpose." Our choices and actions remain under God's control after regeneration. Therefore, although a person is conscious of his efforts and struggles in sanctification, in the end God receives the honor, and the Christian still has no basis to boast of his achievements." - Vincent Cheung, Systematic Theology