You're probably thinking of Jesus' admonition in the Sermon on the Mount, in which He tells us not to worry about the future and what it may hold for us. He said, "Therefore do not worry about tomorrow, for tomorrow will worry about itself" (Matthew 6:34).
Jesus' words have sometimes been misunderstood, as if He were telling us never to think about the future or plan for it. (This misunderstanding may have come from an older translation that tells us to give "no thought" to tomorrow.) But this isn't what Jesus meant. Instead, He is warning us against allowing ourselves to be preoccupied with the future and constantly anxious about it. As He said earlier in the Sermon on the Mount, worrying doesn't change anything; it only makes us tense and keeps us from trusting God.
Instead, Jesus urges us to trust God for the future. He knows our needs and has promised to supply them as we commit our lives and our futures into His hands. God loves us, and He knows what we need far better than we do. The Bible says, "God will meet all your needs according to the riches of his glory in Christ Jesus" (Philippians 4:19).
Most of all, God knows that our greatest need is for our sins to be forgiven so we can go to be with Him in heaven. And He has made this possible by sending Jesus Christ into the world as the final and perfect sacrifice for our sins. Have you trusted Him for your salvation?