See Romans 4:1-8, Romans 11:5-6, Ephesians 2:8-9, and Titus 3:4-7.
You will see that works don't save in the slightest.
The transformation that takes place within a believer (2 Corinthians 5:17) cannot come about by anything we do. It can only come about through trusting Christ to give you a new heart and a new spirit (Ezekiel 36:25-27). It is through faith alone in the operation of God.
Understanding Paul's words:
When Jesus died, He began a New Covenant (i.e. a New Testament) (Matthew 26:28) (Matthew 27:51). This meant that the law had changed (See Hebrews 7:12). We are under a new contract (New Covenant). Romans 4:1-8, Romans 11:5-6, Ephesians 2:8-9, and Titus 3:4-7 are talking about "Works Alone Salvationism" without God's grace. This is because Paul was fighting against "Circumcision Salvationism" (See: Galatians 2:3, Galatians 2:3, Galatians 5:2, Galatians 5:6, Galatians 6:5, 1 Corinthians 7:18-19, Romans 2:28-29, Romans 3:1, Romans 4:9-12, Acts of the Apostles 21:21. Also see: Acts of the Apostles 15:1, Acts of the Apostles 15:5, Acts of the Apostles 15:24).
Anyways, while we are given a new heart with new desires as a part of our spiritual new birth, this does not mean our free will is no ore and we do not need to endure in our faith to continue to be saved.
We need to endure in our faith to continue to be saved:
"But exhort one another daily, while it is called To day; lest any of you be hardened through the deceitfulness of sin. For
we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;"
Hebrews 3:13-14.
"
Blessed is the man that endureth temptation: for when he is tried, he shall receive the crown of life, which the Lord hath promised to them that love him."
James 1:12.
"But
he that shall endure unto the end, the same shall be saved.
Matthew 24:13.
"...
be thou faithful unto death, and I will give thee a crown of life."
Revelation 2:10.
"He that hath an ear, let him hear what the Spirit saith unto the churches;
To him that overcometh will I give to eat of the tree of life, which is in the midst of the paradise of God."
Revelation 2:7.
"He that hath an ear, let him hear what the Spirit saith unto the churches; H
e that overcometh shall not be hurt of the second death."
Revelation 2:11.
"
He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels."
Revelation 3:5.
"
Keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ unto eternal life."
Jude 1:21.
Obeying God or Being Righteous is a part of eternal life:
"
Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city."
Revelation 22:14.
he became the author of eternal salvation unto all them that obey him;"
Hebrews 5:9.
"And, behold, a certain lawyer stood up, and tempted him, saying,
Master, what shall I do to inherit eternal life? He said unto him, What is written in the law? how readest thou? And he answering said, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself. And he said unto him, Thou hast answered right: this do, and thou shalt live."
Luke 10:25-28.
"
Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven."
Matthew 7:21.
"
Blessed are the pure in heart: for they shall see God."
Matthew 5:8.
Every man will be given according to what their work shall be:
"And, behold, I come quickly; and
my reward is with me, to give every man according as his work shall be."
Revelation 22:12.
Sin or Unfaithfulness Can Separate:
"And Jesus said unto him,
No man, having put his hand to the plough, and looking back, is fit for the kingdom of God."
Luke 9:62.
"For
if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins."
Hebrews 10:26.
"For the time is come that judgment must begin at the house of God: and if it first begin at us,
what shall the end be of them that obey not the gospel of God? And if the righteous scarcely be saved, where shall the ungodly and the sinner appear?" 1 Peter 4:17-18.
"
For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire. 2 Peter 2:21-22.
"And
if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book."
Revelation 22:19.
"Behold, all souls are mine; as the soul of the father, so also the soul of the son is mine:
the soul that sinneth, it shall die."
Ezekiel 18:4.
Source used:
Once Saved Always Saved - Fact or Fiction?