This is a fair question, and I hope it shows you the complex nature of God that goes beyond our comprehension. Belief alone, will not get you into heaven. It is the first step and without it you won't get in, even if you live a mostly good life (no one can live a perfect life). God must also come to know you during your time on earth by imaging Christ. Grace made it possible though, because we cleanse ourself in the blood of Christ that allows us to enter the Kingdom without being destroyed. This is made evident throughout the Bible. You must do good works AND accept Christ by loving Him will all your heart, mind, and strength. So if you live a sinful life and reject God until the very last minute, do you get into heaven? Only God can answer that, he can see your true nature, but I would argue no (at first). But this doesn't mean you are doomed either. Hell is another concept many Christians don't seem to fully understand. Hell is the holding cell before your final trial. There is pain and suffering in hell, much like we see in today's world, but that isn't the end judgement. The final judgement comes on the day of the Lord, and if you still have a hardened heart, you get tossed into the lake of fire (which is what the common belief of hell is now). Hope this helps explain somethings!