Grace is not simply leniency when we have sinned. Grace is the enabling gift of God not to sin. Grace is power, not just pardon.
This is plain, for example, in 1 Corinthians 15:10. Paul describes grace as the enabling power of his work. It is not simply the pardon of his sins, it is the power to press on in obedience.
Therefore the effort we make to obey God is not an effort done in our own strength, but “in the strength which God supplies, that in everything God may get the glory” (1 Peter 4:11). It is the obedience of faith.
Paul confirms this in 2 Thessalonians 1:11–12 by calling our acts of goodness “works of faith” and by saying that the glory this brings to Jesus is “according to the grace of God” because it happens “by [his] power”:
To this end we always pray for you, that our God may make you worthy of his call, and may fulfill every good resolve and work of faith by [his] power, so that the name of our Lord Jesus may be glorified in you, and you in him, according to the grace of our God and the Lord Jesus Christ. (2 Thessalonians 1:11–12)
The obedience that gives God pleasure is produced by the power of God’s grace through faith. The same dynamic is at work at every stage of the Christian life. The power of God’s grace that saves through faith (Ephesians 2:8) is the same power of God’s grace that sanctifies through faith.