After reminding the Ephesians of what God had already done for them, the writer then tells them what they are to do in response--good works. You weren't saved by your works; you were saved to work.
Does the promise in verse 8 change when you realize that the "you" is, in Greek, plural? As are the other 2nd-person pronouns in this passage. How hard is it, for us moderns, to read this letter from Paul as being addressed to the church rather than to an individual, that is, the me who is reading it now?
God's gift is salvation. We didn't earn it by anything we did.
Lectio Divina: Ephesians 2:8-9