There are many different opinions about how God works in our lives. There are many different opinions about why God works in our lives. Paul gives a wonderful summation of this idea at the end of 1 Thessalonians:
23 May the God of peace himself sanctify you entirely; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ. 24 The one who calls you is faithful, and he will do this.
God will sanctify us entirely and make us blameless. These two verses open a whole realm of discussion. On being sanctified entirely, you can read more here. On being blameless, you can read more here.
The point, though, is that this is a work that God will do in us. If we endeavor to live for Christ more every day, following his teaching and leading, God will do this. Bit by bit, step by step, grace by grace, and glory to glory we will be transformed by God in this manner.
That is Good News!