From a Lutheran perspective sanctification is God making us holy in Christ. We aren't made holy by our works, we are made holy by the holiness of God in Christ through the indwelling of the Holy Spirit.
"Learn, then, to understand this article most clearly. If you are asked: What do you mean by the words: I believe in the Holy Ghost? you can answer: I believe that the Holy Ghost makes me holy, as His name implies. But whereby does He accomplish this, or what are His method and means to this end? Answer: By the Christian Church, the forgiveness of sins, the resurrection of the body, and the life everlasting. For, in the first place, He has a peculiar congregation in the world, which is the mother that begets and bears every Christian through the Word of God, which He reveals and preaches, [and through which] He illumines and enkindles hearts, that they understand, accept it, cling to it, and persevere in it." - Large Catechism II 41-42
Good works and sanctification come together, but it is not the works which make us holy, it is the Spirit who makes us holy through that which is worked upon us; and encompasses the whole Christian life from its beginning until kingdom come. We are not sanctified by our works, we are sanctified by the Holy spirit who puts us in Christ, and works this through his Church, forgiveness of sin, the preaching of the Word, the Sacraments, and all the way through resurrection and the future life, that "He who began a good work in you will continue that work until the Day of the Lord Jesus". Sanctification, therefore, is a divine work operating upon us and in us.
-CryptoLutheran