Is it possible to really know you'll go to heaven when you die? I've always tried to be a good person, but I worry about whether or not I've been good enough to get into heaven. How can I know?
If our salvation depends on ourselves and our good works — then no, we’ll never have any assurance that God will welcome us into heaven. We’ll always be uncertain, because (as you’ve said) we’ll never know if we’ve been good enough.
But listen: Our salvation doesn’t depend on us and our good works! If it did, no one would ever go to heaven because God’s standard is nothing less than perfection. God is holy, and even one sin — just one — would be enough to keep you out of heaven. The Bible says, “For whoever keeps the whole law and yet stumbles at just one point is guilty of breaking all of it” (James 2:10).
This is why we need Christ, for only He can take away our sins — all of them — and make us acceptable in God’s sight. Jesus Christ was God in human flesh, and as such He was without sin. But when He went to the cross all our sins were placed on Him, and He died in our place. When we come by faith to Him God forgives our sins, and now we can come before Him without fear. The Bible says, “The blood of Jesus, his Son, purifies us from all sin” (1 John 1:7).
Don’t trust yourself and your goodness for your salvation. Instead, trust Christ and His goodness — for He alone is God’s way of salvation. When our faith and trust is in Him, we know we’ll be with Him in heaven forever.