The whole point of creation is through man’s Divine service, we manifest in a revealed way the Divine.
The world was set up in such a way that through our Divine service we reveal the Divine.
Specifically the Jewish people were given the opportunity and ability to do this.
The source of our souls is in the essence of God.
By revealing that your essence is God, you not only save yourself, you save the world.
The way you judge others, negatively, and certainly positively, is the way you are judged.
When we study the Torah, we affect the world, by using the same speech that God used to make the world; but through the benefit, that man puts in his own effort – as we have a Yetzer Hara, therefore the world is renewed in a much higher level.
When we do Mitzvos, we create that the Divine Essence manifests in the matter, in a permanent way.