The reason we cannot save ourselves is because we all miss the mark and fall short of God’s standard of absolute perfection.
Matthew 5:48 “Therefore you shall be perfect, just as your Father in heaven is perfect.”
No matter how good we are, any sin, no matter how trivial it may appear to be, spoils the perfection that God requires.
James 2:10 “For whoever shall keep the whole law, and yet stumble in one point, he is guilty of all.”
Whilst some people are better than others, being better is not good enough. It's like two people trying to jump over a deep canyon. If one falls only a couple of feet short of the other side, he is no better off than the other who only makes it half way.
Because we have all been born into a sin nature due to Adam's failure in the Garden of Eden, not one of us is able to save ourselves. Not one of us is good enough to get into heaven. But because God loves us He sent Jesus to pay the price and offer us eternal life as a free gift.
Why should God offer anyone the gift of eternal life?
Psalm 145:8-9 “The Lord is gracious and full of compassion, slow to anger and great in mercy. The Lord is good to all, and His tender mercies are over all His works.”
Psalm 100:5 “For the Lord is good; His mercy is everlasting, and His truth endures to all generations.”
Joel 2:13c “For He is gracious and merciful, slow to anger, and of great kindness; and He relents from doing harm.”
John 3:16 “For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life.”
Romans 5:6-8 “For when we were still without strength, in due time Christ died for the ungodly. For scarcely for a righteous man will one die; yet perhaps for a good man someone would even dare to die. But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us.”
In fact the Bible says in 1 John 4:8 “... for God is love.”
Because God is a loving God in fact He is just love and He is also merciful, He does not want to punish us. However because He is also perfectly just, He must punish sin! So Jesus became sin for us and took our punishment on Himself in order to save us. God’s love does not overrule His justice.
Deuteronomy 32:3b-4 “Ascribe greatness to our God. He is the Rock, His work is perfect; for all His ways are justice. A God of truth and without injustice; Righteous and upright is He.”
Exodus 23:7c “For I will not justify the wicked.”
Isaiah 13:11 “I will punish the world for its evil, and the wicked for their iniquity.”
Hebrews 9:27 “And as it is appointed for men to die once, but after this the judgment.”
If God were to overlook sin because of His love, He would not longer be just. His law is perfect and His sentence has been passed.
Rom 6:23 “The wages of sin is death!"
However, God in His wisdom has brought His love and His justice together in the person of Jesus Christ!
The Bible makes it clear that Jesus is God and He was fully man and fully God and He took your place at Calvary, and now expects us to take our place in the heavenly realm.
Eph 2:6 Amplified Classic Edition And He raised us up together with Him and made us sit down together [giving us [a]joint seating with Him] in the heavenly sphere [by virtue of our being] in Christ Jesus (the Messiah, the Anointed One).