God's completed work is necessary and sufficient
"For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God— not by works, so that no one can boast.
For we are God’s handiwork, created in Christ Jesus to do good works, which God prepared in advance for us to do."
There is an old saying which goes something like this: "If something seems to good to be true, then it's probably not true."
God's gift of grace doesn't fit easily and comfortably within our normal paradigms.
In this world, things are earned. Minerals and crops are extracted from the earth with great planning and effort. Paychecks are the result and indication of hard work. Babies are carried and born through pain and families are raised through commitment and sacrifice. And on, and on...
What in the world does grace have to do with anything?
It's only natural to think that approval from God would be earned also. However, in His holiness He maintains a standard which for us is unattainable. It's is beyond the ability of mortals -- like trying to jump to Mars.
Instead, we gain His acceptance and approval through His grace -- His kindness and favor towards us which is unearned, undeserved, and initiated by Him. It was His will and His pleasure to pay the fee or the fine required to reconcile fallen and rebellious mankind back to Himself.
For us, it is a free gift that we receive freely on the basis of faith in His promise and faith in the Giver.
Our good deeds do not qualify us as good enough. No one weighs our good works against our bad ones, our merits against our transgressions, our victories against our defeats, or our strengths against our weaknesses.
The requirement for God's approval is absolute purity and holiness, and none of us makes it.
We need a mediator to advocate for us and that atoning sacrifice is Jesus.
Yet, we are His workmanship. He has established good things for us to do after we have accepted His gift, and these things will bring glory to Him.