Twice every seven years a Jew living in Eretz Yisrael would be required to make a declaration (before Hashem) known as viduy ma'asrot.  The farmer would begin with "I have removed the Holy things from my house" and proceed to declare that he had successfully separated and distributed ma'aser and all other obligations, carefully observing the intricate halachic requirements of each mitzvah (Devarim 26:13-15).
 
We associate the word viduy with confession for our sins, especially this time of year, as we anxiously await the period of selichot culminating with Yom Kippur when we recite viduy ten times.
 
Viduy is a prerequisite to teshuva, repentance, which included the dramatic offerings of the Kohen Gadol on Yom Kippur. Given that we associate the word viduy with the confession of our sins, we can't help but wonder how viduy is connected to having properly fulfilled the mitzvoth of tithe removal from our produce.  Viduy, as far as we know, implies realizing our shortcomings, while here we are declaring that we properly observed Hashem's commandments.
 
Rav Ovadia Sforno (16th century) gives an insightful explanation as to why Chazal refer to this declaration as viduy.  Due to our sins, Divine service was taken away from the firstborn and given to the Levites. Had it not been for our sins, the phrase, "I have removed the Holy things from my house", would be inappropriate, as we would not have to remove the sanctified portion of the produce from our homes. The holy people would eat their sanctified foods in every Jewish home.
 
While it may be true that the actual words of the viduy maaser includes only that which we did correctly, the entire institution and practice is the result of our shortcomings.The fact that the Kohen has been removed from each Jewish home has brought about a fundamental change to the nature of our homes. Imagine what our homes would look like if a member of each family was a true spiritual leader, spending a few weeks each year serving in the Beit HaMikdash.
 
Although the Kehuna no longer belongs to the firstborn of each family, a remnant of the original system still remains with us.
 
Tosafot Baba Batra (21a) expound the well-known verse"Ki mitziyon tetze Torah" - "from Zion will the Torah come forth" (Yeshayahu 2:3) by quoting a Sifre (which we do not have) on the pasuk:
 
"and you shall eat before Hashem, your G-d, ...the tithe of your grain, your wine, and your oil, ...so that you will learn to fear Hashem, your G-d, all the days" (Devarim 14:23).
 
"This teaches us that Maaser Sheni brings us to Talmud".
 
 How so?
 
Imagine a farming family of old, that sends off one member to Jerusalem with a truckload of Ma'aser Sheni produce, which must be consumed within the holy walls.  At least one family member would spend a considerable amount of time in Yerushalayim eating Maaser Sheni, perhaps bringing Korbanot.  While there, he would observe the Kohanim performing their holy service. He would be exposed to, perhaps even study, in one of the glorious Torah academies. This would inspire him greatly to fear Hashem and study His Torah. Upon returning home, this inspiration would spread to the entire family and community.