The time-tested summary of our Christian faith:

The Apostle’s Creed I believe in God, the Father almighty, creator of heaven and earth. I believe in Jesus Christ, his only Son, our Lord, who was conceived by the Holy Spirit and born of the virgin Mary. He suffered under Pontius Pilate, was crucified, died, and was buried; he descended to hell. The third day he rose again from the dead. He ascended to heaven and is seated at the right hand of God the Father almighty. From there he will come to judge the living and the dead. I believe in the Holy Spirit, the holy catholic church, the communion of saints, the forgiveness of sins, the resurrection of the body, and the life everlasting. Amen.

On a personal level, the Heidelberg Catechism says it best:

Heidelberg Catechism, Q&A #1 Q. What is your only comfort in life and in death? A. That I am not my own, but belong—body and soul, in life and in death—to my faithful Savior, Jesus Christ. He has fully paid for all my sins with His precious blood, and has set me free from the tyranny of the devil. He also watches over me in such a way that not a hair can fall from my head without the will of my Father in heaven; in fact, all things must work together for my salvation. Because I belong to Him, Christ, by His Holy Spirit, assures me of eternal life and makes me wholeheartedly willing and ready from now on to live for Him.

It's all in the Bible:

God acted first in creation. (Gen 2:15-17) Humankind rebelled—sinned. (Gen 3:6-13) Sin is a powerful force that separates all humankind from a Holy God. (Romans 5:12-14, Isaiah 59:1-2, Romans 3:10 & 23) God’s grace is bigger than our sin. (Matthew 19:25-26, Titus 2:11, 2 Peter 3:8-9, Acts 10:34-36, Romans 10:13Romans 8:38-39) God bridged the separation with His grace through Jesus. (Isaiah 53:5-6, John 3:16, Romans 5:8, 1 Peter 3:18, Romans 10:9-10, John 1:12) Jesus is the only way to reconciliation with God. (John 8:24, John 14:6, Acts 4:12, 1 Timothy 2:5Hebrews 7:25)