You are partly right; bad things certainly do happen in this life. But sometimes they happen to good people who don't seem to deserve it, while bad people sometimes escape with hardly a scratch. How do you explain this, if God's judgment is only limited to this life (as you believe)?
The Bible, however, paints a different picture, for it tells us that in eternity all the injustices and evils of this world will be judged. Someday every nation and individual will stand before God, and to those who have ignored or disobeyed Him, He will say, "Depart from me, you who are cursed, into the eternal fire prepared for the devil and his angels" (Matthew 25:41).
Those are sobering words, and it would be foolish (as well as dangerous) for us to ignore them. Hell is real, the Bible says—just as real as heaven. No, I don't know exactly what hell will be like—but not one word about it in the Bible would ever make me want to go there. Jesus called it a place of "darkness, where there will be weeping and gnashing of teeth" (Matthew 22:13).
But listen: You don't have to go there! God loves you, and Christ came to open heaven's door for you. Only one thing will keep you out of heaven, and that is your sins. But on the cross Christ took upon Himself our sins and the punishment we deserve. Don't let another day go by without Christ, but by faith give your life to Him and trust Him alone for your salvation.