The portion of Nitzavim speaks about unity. In the beginning, it says "you are standing here today..." Using second person plural tense, it then changes to second person singular, and finally ends with singular tense.
The change of tenses occurs in order to show us that the Israelites need to be unified on all levels in order to merit taking over the land of Israel. But in order to merit being part of that re-entry, Shem Mishmuel (a nine-volume collection of teachings on the Torah) says we need to have certainty.
Although the generation that left Egypt saw all the miracles and wonders that the Creator manifested, today we aren't able to see even the smallest of miracles around us. We need to be able to have certainty, and reach a critical mass of people who will understand that only through certainty can we bring the redemption.
It is very hard for human beings, when we are trapped in the physical environment, to have certainty. In this portion, we have the tool of prayer, which our forefathers established to help us connect and fill that spiritual void that keeps us from having certainty.
Through prayer, we can break any of our walls and connect to the Creator – even when it seems that there is darkness. But, in this portion, we also see that no longer will it come for free like it did for the generation that left Egypt. Instead, we have to work to earn our certainty in the Creator and for our place of unity with the masses, so that we will bring the end of pain and suffering to the world.