The flow of the narrative in Parshas Nitzavim stresses this: And Hashem will circumcise your heart. Teshuva requires a change of personality, a circumcision of the heart. An insensitive, stubborn heart must be transformed to a sensitive one. This requires great character and fortitude. The Torah continues saying that this mitzvah (according to Ramban, the mitzvah of teshuva) is not distant from you, nor is it in the Heavens. No matter how steeped in sin, no matter how great the temptation to perpetuate your successful and sinful life, you can return to Hashem by taking advantage of the miraculous opportunity provided by teshuva. The Torah continues: Behold I have placed before you, life and death: choose life. It is your decision. If you decide on life you can attain life, through repentance.
These are the two types of bechira mentioned in Parshas Re’eh and in Parshas Nitzavim. In Parshas Re’eh the Torah tells us about the bechira to adhere to the commandments of Hashem and refrain from sin. In Parshas Nitzavim, the Torah tells us that we have the choice to repent after we have sinned.
The second interpretation, according to the Rav, was alluded to by the Haamek Davar. In Parshas Re’eh, Moshe demands that the people comply with the obligation to perform mitzvos. They must observe Shabbos, kashrus, etc. Some people will give in to their passions and transgress, but most reasonable people would come to the conclusion that it is preferable to live a righteous life than a sinful life, and they would therefore comply with the mitzvos. Thus, in Parshas Re’eh, the Torah is not demanding anything superhuman from the individual.
In Parshas Nitzavim, the Torah requires the people to listen to what Moshe is commanding them, and to love Hashem. According to Rambam (Moreh Nevuchim), ahavas Hashem, love of Hashem, requires total dedication to Hashem. Everything I do and say must be dedicated to Hashem. I may not relinquish this dedication for even an infinitesimal fraction of a second. This is a very lofty and demanding standard. People may despair of ever attaining such a level.
In Parshas Re’eh Moshe told them not to despair, they can attain it. Not only is bechira effective in accepting the performance of mitzvos and refraining from sin, it can also help man attain the highest levels of religious life, d’veykus b’Hashem, clinging to Hashem, and ahavas Hashem, love of Hashem, if man desires it.
Rambam says (Teshuva 5:2): Every man has the potential to be a righteous individual, on the level of Moshe our teacher. One might think that Moshe’s level of righteousness, the greatest of all men, would be unattainable. However through bechira and dedication, Moshe’s level of righteousness is indeed reachable.
Chasssidim say in the name of Reb Zusha Anapoler that when he passes on and appears before the heavenly court he will not be asked why he did not attain the level of Moshe Rabbeinu. Rather, he will be asked why did he not attain the level of Zusha, to fulfill his potential.
The Rav said that this disagrees with the above-mentioned Rambam. According to Rambam, since man has the ability to attain the level of Moshe, he will be judged by that standard. He will be judged by the degree to which he is davuk b’Hashem, how close he clings to and loves Hashem. This is up to man to decide, based on the concept of bechira in Parshas Nitzavim.