If we are walking with God by definition we are not complacent. It is when we are not in fellowship with Him that we are in danger. We are to abide in Him, John 15:1 – 16. We are to stay vigilant, 1 Peter 5:8. If we are doing that, by definition we are walking with Christ and not complacent.
I find that it is when I have drifted away from the disciplines of discipleship, complacency steps in.