The reason for "good works"

Paul makes clear, repeatedly, that we do good works not to earn God's favor. Indeed, God's favor is a free gift that we neither earned nor deserved. In Ephensian 2:8-9 (KJV), Paul states,

For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.

So then where do good works fit into a spiritual life? In verse 10, Paul explains,

We are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.

So good works do not cause us to enter God's favor. Rather, the fact that we have God's favor causes us to walk in obedience. This reversal of the cause/effect relationship between works and salvation is a central part of Jesus' teachings, and Paul expands upon it in his letters.

So in our prayers, let us thank God for our undeserved salvation, and then let us walk in obedience as a sign of our thankfulness for that salvation.