A Hasidic rebbe instructed his students to abandon a project (building a mikveh) part-way because there was no opposition. “If there is no opposition,” said the rebbe, “there is no holiness. If you desire to sin, the world gives you no opposition. It is only when you want to do a mitzvah (divine commandment), that you get opposition.”
Then the rebbe got a critical letter about his project and armed with that opposition, he had his students complete the project.
