teshuva, as is stated at length in the early sefarim.
The Final Shabbos:
Chazal say (Rosh Hashanah 2:2): “One day of a year is considered to be a full year.” The Bais Avrohom states: If during the course of an entire year, one only spent one day serving Hashem, his entire year is saved. This is true even if it is the very last day of the year, and certainly if it is the last Shabbos of the year. This one day can uplift the entire year.
On Erev Rosh Hashanah, One Can Still Save Himself:
The Rov of Freiman zt”l (quoted in Sefer Erez Balevanon) relates that one year, during the recitation of Selichos on Erev Rosh Hashanah, the Minchas Elazar of Munkatch zy”a turned around to face the kehillah. Several times, he repeated the words of Selichos: “If only you would all return with heart and soul to your legion”, and said, “Now is the time. We can still save ourselves from purgatory.”
Later on, when they were reciting the words: “If you arrange your atonement over the many times and days”, he said: “If you arrange your atonement... But it is only because of the ‘many times and days.’”
In other words, the only reason why people do not do teshuva properly is because of the lengths of golus.
Minchah on Erev Rosh Hashanah Can Bring the Geulah:
We even find that at the time of Minchah on erev Rosh Hashanah, when the day is almost over, one can still do teshuva.
My grandfather, the Kreitchnifer Rebbe zy”a (Kol Emunah, Parshas Eikev 5747) quoted the pasuk (Devarim 11:12): “The eyes of Hashem your G-d are on it from the beginning of the year (hashana) until the end of a year (shana).” He said in the name of his grandfather, the Yitav Lev zy”a (Parshas Bo) that this means that at the beginning of the year, people tend to believe that this will be “the year” (hashana). They are certain that this will be the year for salvations and redemption. But when the end of the year arrives, they see that it is only “a year” (shana) that was the same as all other years.
My grandfather explained the verse in an alternate way. He understood the words “the end of the year” to be referring to the final Minchah right before Rosh Hashanah. The pasuk is saying that one should not stop doing teshuva and davening for the geulah until the year is completely over. It is still possible that this will be “the year” when we merit the redemption.
May we all merit a kesiva v’chasima tova and a year of blessing and redemption.