We have mentioned the saying "Better one hour of repentance and good deeds in this world than all the life in the next world."
As a figure of speech, what is being expressed is that in the performance of mitzvot, or in living a life according to Torah, a person acts as a sort of extension of the manifestation of Divine Will.
He is participating, that is, in Revelation, whereas at any other level of being, even in any world above, he merely enjoys the radiance of the Shekhina.
The reason for this apparent exaggeration of the power of a mitzva lies in the recognition of the fact that only God encompasses both aspects of reality: that which is and that which is not, this world and the world beyond.
Just as we are convinced of the substantial existence of this world, so does the world above view us as a nothing, seeing itself as the genuine reality.
In illustration of which there are certain clever drawings with subtly shifting fore, grounds and backgrounds.
The viewer is never quite sure which is the real picture.
So too, the world below and the world above can be portrayed as a cosmic optical illusion, each fitting perfectly into the other and providing us with either the real against the unreal, or the front against the back, constantly changing places in our consciousness.
It is not only the old problem of subjectivity of vision.
It is primarily the comprehension of the nature of reality itself, a recognition of the existence of a higher and a lower, a world of the graspable and a world of the ungraspable, being and nothing.
–Rabbi Adin Steinsaltz
From "Implications of the Menorah" in The Candle of God by Rabbi Adin Steinsaltz