Musar על ברכות 56:10

The quality of shame is a fence and an iron partition between a man and all manner of sins, for a man may commit many sins in private that he would be ashamed to do in public. An example cited by our Sages: "When Rabbi Johanan ben Zakkai was about to expire, his disciples said to him, 'Our teacher, bless us!' And he said to them, 'May the fear of Heaven be upon you as much as you fear human beings!' They asked in wonder, 'Shall we indeed fear God only as much as we fear human beings and no more?' Whereupon, he said to them, 'Would that it were so, If only you would realize that when a man commits a sin he thinks "I hope no one sees me," (Berachoth 28b). All because he is afraid of being disgraced in the eyes of people, and this fear of disgrace often restrains him from doing a sinful act. Eventually, he will refrain from doing a sinful act from nobler motives (Pesahim 50b).