Why should we be good?

What's the reason for us to act good or bad in any given situation. What defines good? If there were no consequences for anything would we still try to act good towards others? If there was no law against stealing, would we steal? I believe that if there isn't a final judgement than there can not be true goodness in this world. Goodness would have no meaning if there was no consequence. What stops us from doing bad things in privat or in the hidden? Why should we feel bad about doing something horrible when hidden? If there is no final judgement then the line between good and bad gets erased and they both have no meaning at all and everybody should just do whatever they want. However I believe this goes against human nature, we are all born with an inate sense of what is wrong and what is right. Only an eternal judgement gives essence to right and wrong, good and bad. Otherwise these are just functions of society constructed to rule us without a real definition anything can be bad and anything can be good there would be nothing that separates them. What are your thoughts on this?