if you don't believe in an afterlife or judgement day or going to heaven/hell... wouldn't that encourage a sense of earthly justice and make you more moral instead? how sad would it be if we lived a certain way due to the fear of punishment/reward in our afterlives?
and what's the big deal, you repent and you're in the good books again. it's just a religion based on not taking responsibility for your own actions.
also moral values are not unique to religion... love your neighbours, honour and respect your parents, don't do to others what you would not want done to you. this "christian" sense of morality had already been conceived by confucius who lived hundreds of years before jesus.