In the Pirkei Avot ("Sayings of the Fathers"), a familiar tractate of the Mishnah, there is a statement to the effect that one hour of happiness in the world to come is better than all the life of this world.
Such a belief may satisfy the mystical ardor of many religious people.
But this statement is followed by another—a very baffling opposite to the first- declaring that one hour of teshuvah (repentance) and maasim tovim (good deeds) in this world is worth more than all the life in the world to come.
This is to say that we, in this world, have something no other world contains: we can come into direct communion with God through His Torah.
When we study Scripture, God studies with us, the Talmud says.
When we perform actions according to the Torah, we are not separate from Him.
Learning is therefore not just an intellectual tie; the more one understands, the more one is connected.
Understanding requires a lot of discipline, of the emotions as well as of the mind.
The intensity of all thought and feeling has to be contained and directed.
Therefore, too, the Torah has its many parts, allowing for a healthy organic life within the tradition.
But as with anything of such an organic wholeness, the parts are also interdependent.
A faulty part can put the whole thing in danger of breakdown.
If the whole thing is, like one of the modern rockets, a vehicle to heaven, a flaw in any one small component can prove disastrous indeed.
–Rabbi Adin Steinsaltz
From On Being Free by Rabbi Adin Steinsaltz