If you have the ability to accept or reject God's grace, then you are the ultimate arbiter of your salvation because you have the final yea or nay.
God offers, but man determines.
That's not what Scripture says. Read it again.
Not of works, lest any man should boast. For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them." -- Eph. 2:8-10"For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: