Ephesians 2

Paul makes it clear that -

"For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast."  (Ephesians 2:8–9)

Obviously, by grace and the infinite atonement of Jesus Christ that can be saved.  We cannot do it on our own.  But at the same time -

"For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them."  (Ephesians 2:10)

Which suggest to me that His grace is conditional.  Thus we are justified by grace.