It’s not follow his rule or be doomed. God isn’t some monster who wants us to earn his love. He isn’t watching from heaven, waiting for us to do something wrong so He can catch us. Some religions see God that way, but they are wrong. That isn’t who God is. God loves us.
It’s choose to love Him as best you can, and try your best to follow His will, or choose to reject His love by sinning and by rejecting the one who made and loved you be unhappy. If you choose up the last moment of your life to reject Him totally and completely, then when you die, you will choose hell. (I will explain why you would choose hell in a moment) If you repent, then no matter what you’ve done, or not done, God will forgive you. He is always offering us forgiveness. But we have to accept it. He won’t force it upon us, precisely because He gave us free will to choose whether to do good or bad.
Hell is being completely away from God, because that person chose to not love God. God doesn’t send the person there. They choose it. Why would someone choose hell? Because that person will have destroyed him/herself to the point that there is no way for him/her to be happy at all, and to be in heaven would be worse torture than being in hell. Why would heaven be worse for that person? Imagine spending all of eternity with someone whom you have completely rejected, someone you hate. That is what heaven would be for the person who chooses hell.
Imagine this: You have a friend and that friend does something very bad to you. You immediately say that you will forgive him, but he says “no I don’t want your forgiveness.” Then people blame YOU for that friend’s unhappiness. By our refusal to repent (turn away from our sins), we are saying to God, “I don’t want your forgiveness.” It makes as much sense for them to be mad at you in this situation, as it does to blame God for people being in hell.