If you've been born physically of the flesh, and then born again of the Spirit by receiving Jesus' pardon for your sins, then you die only once--physically. But if you've only been born once, just physically, you're going to die twice! First the natural physical death; second the spiritual death, "the second death"! (Rev.20:14)
Christ's death was far worse than mere crucifixion and the physical agony that He was suffering. He was suffering the spiritual agony of the lost sinner dying for his sins, without Salvation, without God! Only in His case He wasn't dying for His Own sins, He was dying for the sins of the world!--Yours and mine! He did that so you won't have to go through that horror of dying a sinner's lonely death!
Those who reject Christ's atonement have to suffer for their own sins. But those who receive Jesus now are completely forgiven and completely relieved from the punishment of sin. "For the blood of Jesus Christ cleanses us from all sin!" (1Jn.1:7)
So make sure you're born again, and you'll die only once!--Then you go to be with the Lord forever!