Parshat Devorim begins the book of "Mishne Torah". This Shabbat is also know as "Shabbat Chazon".

"On the fortieth year, on the first of the eleventh month" (first of Shevat), a little more than a month before he passed away, Moshe reviews Hashem's Torah and gives words of Mussar to the new generation.

Moshe was speaking, not to the Dor Deah, the generation of knowledge who experienced the exodus; and not to the generation who witnessed Kriat Yam Suf and Matan Torah. That generation was gone; perished in the desert as was decreed by HaShem after the sin of the spies who doubted HaShem's ability.
The generation Moshe speaks to is a younger generation who will soon be entering Eretz Yisrael. To this generation who did not see, but only heard, of the great miracles and the great revelation on Mount Sinai, Moshe had to give his best and last effort to give words of Tochecha (reproof). And he did so at the most effective time, right before his death (see Rashi)- a time when no one can accuse him of any ulterior motive, a time when Moshe was standing between Shnei Olamot, this world and the world of truth. When speaking to this generation, it seems, one who had not actually seen miracles and revelations, Moshe had to do more convincing.

Moshe uses the word "Eicha" which stands for Tzaros and tragedies. "Eicha" How can I carry your burden, etc... Rashi comments on "Masaachem" (burden) stating that they were Apikorsim; heretics or non-believers.

How does Rashi derive "non-believers" from the word "burden"?

Rav Nachman of Breslev explains this beautifully. He says, "it's much more burdensome to be a non-believer". An Apikoros who doubts everything has the burden of explaining everything around his world, whereas a believer has only to say "it is from HaShem".

This generation who did not see is probably more doubting than the previous generation who did see. It is, therefore, more pertinent for Moshe to warn, reprove and encourage them not to lose their Bitachon in HaShem than it would have been for him to do the same for the previous generation- who did see.

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By the way, it is interesting to note that this is one of only two occasions when Moshe spoke to "Kol"- all of Israel, the other being in Parshat Vayakhel. Since Kol has the dual meanings of all and every, the use of the word suggests that his message was meant for every one of us; not only was Moshe speaking to his generation but to Kol Yisroel- to all future generations as well.

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For a Tochecha- a reproof- to be effective and meaningful, it must come lovingly. As the Midrash says: "Reproofs should have come from Bilaam and blessings from Moshe. Why is it reversed? Had the reproof come from Bilaam, Israel would have said, `it's just an enemy talking' (pay no attention to him). Had the blessings come from Moshe, the other nations of the world would have said, `they received a blessing from someone who loves them' (it's insignificant). Therefore, said HaShem, `let the reproof come from Moshe who loves them and the blessing come from Bilaam who hates them'."
In his love and respect for his people, Moshe did not embarrass them. He reproved them only through a remez, a hint. They understood what he meant and were not embarrassed.

In his reproof, Moshe reminds his people of their lack of faith as demonstrated by the sin committed by the spies. He states, "and you sat and cried before HaShem" (Bamidbar 1:45). This crying as the Gemorah Sanhedrin (104) says, took place in the month of Av. HaShem said to Israel, "since you have cried for nothing, I will therefore establish this night as a night of crying for future generations." Sitting and crying implies that they cried at least twice; thus future generations will also have to cry twice, as the destruction of both Holy Temples took place on this date.

Moshe hinted that one "Eicha", one sin of Apikorsus and the lack of belief about the promised land will lead to future "Eichas"; tragedies and destructions of Eretz Yisrael.

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The Jerusalem Talmud (Yoma 1.1) states the following: "A generation that did not merit to see the Holy Temple rebuilt, is regarded as if it itself destroyed it."
Rav Levi Yitzchok of Berditchev says that the reason this Shabbat is called Shabbat Chazon is because the word Chazon means "seeing"; every Jewish Soul "sees" the third Holy Temple and is awakened by this vision. Our souls long for the rebuilding of the Temple and for its glory. The Rebbe illustrated this through a parable of a father who had a beautiful suit made for his son who promptly tore it. The father then made him a new one; but the son tore it again. The father then made a third suit and showed it to his son but did not give it to him until such a time when he learned how to properly treat his beautiful suit.
We too are "shown" the third Holy Temple every Shabbat Chazon.
All we need to do is earn the merit to have it rebuilt in our time.