The third Lubavitcher Rebbe, Rabbi Menachem Mendel of Lubavitch, was once asked the following:
“What is the point in toiling in the study of Chassidus? For, when Moshiach comes, the depth of Torah will be revealed. Everyone will study it, even those that did not learn it now.”
The Rebbe responded with the following allegory:
“When a person is standing outside a room and overhears a conversation that is taking place on the other side of the wall, although he doesn’t understand the entire conversation, he catches a word here and there. If afterwards he is told the content of the conversation, he’ll say to himself, “Aha, aha,” as he now understands what he overheard.
The same is true pertaining to the study of Chassidus. A person who hears it for the second time understands it a lot clearer than a person hearing it for the first time…”
 Otzar Pisgamei Chabad, Vol. 1, Pg. 414