Philippians 2:13

for it is God who works in you, both to will and to work for his good pleasure. (Philippians 2:13, ESV)

Why do we work out our salvation? Why would we take that salvation that God has freely bestowed on us and work it out into the rest of our lives? Why would we work it into our homes, our families, our work places, our friends, our churches, and our neighborhoods? Why? It is because (for) God is working in us on two levels: the will and the work.

For many, the thought of God's sovereignty in our lives seems to be a dis-motivation toward effort. In the scriptures, this is never true. Anytime a biblical author discusses God's sovereign hand in our daily lives, it is a motivation to even higher effort. This can be noticed in evangelistic efforts: Paul the Apostle, after a discouraging time in ministry, was motivated by the Lord to continue his efforts because the Lord told him that, "... I have many in this city who are my people." (Acts 18:5-11)

If you look at God's sovereign hand at work in your will and in your work, and it doesn't encourage you, then you must be looking at it wrong. It ought to be, the way it was for those Biblical characters, an understanding that you will be given the exact success that God has foreordained for you.