A persons single, limited action effects only a minor change in the whole of reality.
On his own, he is incapable of transforming every etrog in the world into one with which a mitzva is performed, nor does he have the ability to convert every strip of hide in existence into
a parchment on which a Torah scroll is written.
But the truth is that there is no need for him to do so.
Everything in the world is interconnected, every element drawing others along with it.
The ripple effects of each isolated action in this world are felt far beyond its epicenter, and so when a person alters even one particular detail in the world, he thereby affects everything of a similar nature.
The totality of existence is elevated along with its particularity.
Rabbi Adin Steinsaltz