Whether or not you believe in God is immaterial. Your opinion doesn't change facts.
If God exists, then He has created everything to His purpose; and we're part of it.
But when we stray from that purpose, then He will exercise the right inherent of a creator to do what He will with us.
Have you ever lied, stolen anything without asking, looked upon the opposite sex with lust in your heart, or hated someone? If you did any of those things then you are what you've done (1 Corinthians 6:9-10 & James 2:10).
You are a liar, a thief, an adulterer, and a murderer, ... and more. For those are only four of the 10 Commandments. If you go to a courtroom, you might ask the judge "Please pardon my crime; I know I've killed someone but I've done good all my life. I promise never to do it again".
Would a good Judge pardon you, or carry out the sentence because he is good?
Jesus Christ, the God the son, came down as a man (John 1:1-3, 14). God can only admit to Heaven the righteous and not the sinners (Psalm 5:4 & Romans 2:6-7) but Jesus lived by the commandment none of us can keep perfectly (Hebrews 4:15), and then died in our place of judgment (Romans 5:8), and rose again from the dead (John 20 & Acts 1:11),
Because He did that, we can come to Him by Faith Alone. Not by the good deeds we've done but by placing our trust on His promise, we will be saved (John 5:24). Eternal life is yours if you repent of your sins, and believe in Christ and His Gospel (Mark 1:15 & 1 Corinthians 15:1-4).
You know that you're saved if you hate the sins you loved and loved righteousness that you once hated (Romans, 8:6-7, 2 Corinthians 5:17, & 1 John 3:6-9).