Being better behaved than most? It's not like God has to grade on a curve.
Does a person love and thank God purely? Do they even live up to the rules they apply to others?
No
We will never be 'perfect'. But we are told that we can trust in God's forgiveness to make up for the inability, so long as we are willing to admit to our flaws and failures, and keep trying.
Also, it's not really about 'good or bad behavior', it's about the state of mind and heart that fuels the good and bad behavior. When we consistently and persistently allow the spirit of fear, greed, and selfishness to govern our thoughts and behaviors over the course of our lifetime, this spirit poisons us, and becomes us. And we can never recover. (Thus, we fall into an eternal hell of our own making.) But if we are willing to recognize this shortcoming within ourselves, and keep trying to think and act on the spirit of love, forgiveness, kindness and generosity, that also exists within us (this spirit being called the "Christ within"), doing so can heal us and save us from ourselves. And act as an antidote to that poison that would otherwise condemn us for all eternity.
Religious Christianity is not just about eternal punishment, it's also about how to be saved from that eternal punishment. And the key is to understand that we have the power to choose. Thus, we are responsible for the ultimate result. Not God.