God says in His Word  that you can KNOW!
I John 5:13 
I write these things to you who believe in the name of the Son of God so that 
you may know that you have eternal life.

Sin separates us from God...
Romans 3:23...for all have sinned and fall short of the glory of God...
Isaiah 59:2
But your iniquities have separated you from your God; your sins 
have hidden His face from you, so that He will not hear.

No one is perfect...
Romans 6:23
For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.
Hebrews 9:27
Just as man is destined to die once, and after that to face judgment...

The measure of God's Love?
II Corinthians 5:21
God made him who had no sin to be sin for us, so that in him we 
might become the righteousness of God.
Romans 5:8
But God demonstrates his own love for us in this: While we were 
still sinners, Christ  died for us.
John 3:16
For God so loved the world that he gave his one and only Son, that
whoever believes in him shall not perish but have eternal life.
Paid in full! Your sin is covered by the precious blood of Jesus Christ!   
John 3:36   
He who believes in the Son has everlasting life; and he who does  
not believe the Son shall not see life, but the wrath of God abides on him. 
Acts 16:30   
  He then brought them out and asked, "Sirs, what must I do to be saved?  
Romans 10:9, 10   
  That if you confess with your mouth, "Jesus is Lord," and believe in your heart that God     raised him from the dead, you will be saved. For it is with your heart that you believe   and are justified, and it is with your mouth that you confess and are saved.

Help me, God!