On one occasion—it was Rosh Hashanah of 5641 (1880)—Rabbi Shmuel of Lubavitch said:
In truth, we could be rid of the oppressors of Israel. But the Jewish people prefer the bitter medicine.
There are two types of medicines: sweet medicines and bitter medicines. The problem with a sweet medicine is that when it is administered to a child, the child wants more; the child does not understand that he is ill and that this is medicine. With a bitter medicine, one at least knows the truth.
Cited by the Rebbe in HaYom Yom, vol. II (unpublished)