What does it take to earn eternal salvation?
There's no Bible scripture that requires good works as a payment for salvation. Just like no one does anything to be conceived and born into the world. Salvation is being spiritually born again from above. It is by faith. Not of works lest anyone should boast in their good work achievement. Or no handing out of a plaque or award to certify your achievement.
Salvation happens only by believing that God sent his son Jesus to pay the penalty of your sin. Having wiped your slate clean. Being delivered out of the authority of darkness and translated into the kingdom of God's dear son in whom is redemption and forgiveness of all sin. Receiving a spirit of adoption being a child of God, accepted in the Beloved. Being equally loved by the Father as much as he loves Jesus.
If you think you know the answer, are you sure?
The assurance of salvation is by the Holy Spirit who knows the truth and conveyed it to the servants of God in the old and new Testaments.
He gives witness in the believers heart of being saved. That's what 'knowing' is concerning the Bible text that says "Know the Lord". The word denotes a personal experience in having entered into a personal relationship with Jehovah Elohim.
If you aren't sure, could you do more?
Salvation isn't earned. No sinner could do enough good things to gain salvation. The good deed that Jesus did for all mankind was in being the Lamb of God to be slaughtered and his blood to wipe away all sin.
No sinners blood could save them. The other two sinners on either side of Jesus during the triple crucifixion.. their deaths alone did not result in their salvation. It resulted in one going to hell while the other putting faith in Jesus was given the promise that he'd be in Paradise/heaven.
A sinner has no ability to gain salvation when they have no righteousness. If Abraham were to do works to gain righteousness it's said that he'd have nothing of gain before God.
A sinner doing good in hopes to gain salvation is like expecting a poverty stricken, bed ridden, mentally deficient, retired person to pay off the USA debt. It's just impossible.
It's like a husband who is so old that he can't father a child and his wife barren all her life can't conceive a child.. it's impossible.
If you could do more, why aren't you?
If?.. there is nothing more to be done. God knows the problem and he knows the solution. God supplied the only righteous one. His son Jesus who is capable of doing the good work that sinners are spiritually incapable of doing for themselves much less for everyone else.
Jesus gave of himself so that sinners who knew no righteousness would be made righteous. While he who knew no sin was made to be sin because he completely took our place while He was on the cross.
It was done to demonstrate God's love through Jesus Christ who loved us and so gave himself for us.
Here are two questions- One. Could any sinner say that they are doing a good work to show that they love God?
No. They think that they can do a good work to ingratiate themselves to God. Their motive is selfishness.
So here's a rhetorical question.. Why would they think their good work is a way to gain salvation?