Those who start on the negative are welcomed by the other-side that brings impurity on them. Impurity stays on a person in this world and the world to come, until it is corrected and purified.
When a person wishes to purify himself, he gets the necessary support from the pure system. While the person is on the path of purity, the impure spirits lose control over him.
“לֹא תְאֻנֶּה אֵלֶיךָ רָעָה וְנֶגַע לֹא יִקְרַב בְּאָהֳלֶךָ.”
“No evil will befall you, Nor will any plague come near your tent.”
Rabbi Yossi explains that ‘No evil will befall you’ is about protection from Lil-th. She is the female of the negative side and influence us to follow the evil inclination. ‘Nor will any plague come near your tent’ is a protection from all other negative forces.
The moon was created without the ability to have full light. This lack of light allows the impure spirits to have control at night. Rabbi Elazar says that because of that, we should not walk alone at night. The evil (רָעָה) is the Snake and the plague (נֶגַע) is Sam-l who is the minister of the other side that rides the forces of the Snake and inflict judgments on people.
From sundown to midnight is the time when the other side is in full control and we should follow Rabbi Elazar’s advice. After midnight the light begins to grow up and it’s a good time for studies and meditation that would bring us protection during the coming day and beyond.