Simcha Minute by Rabbi Avigdor Miller
Even when the gentiles were at their best, in their private lives they did many wicked things that no one knew about. But the Torah trains people to practice self-control at all times, even in secrecy.
That is essential. If a person will only behave decently in public but will commit all kinds of things in private, he will certainly not succeed in the Next World. He won’t even succeed in This World. — Ohr Avigdor Shaar Avodas Elokim