The impending din of Rosh Hashana and Yom Kippur focuses our attention upon [the need for] teshuva. This is obviously entirely appropriate and commendable. The problem is that we inappropriately associate teshuva exclusively with the din of Yomim Noraim. This distorts the mitzvah of teshuva in two crucial, interrelated ways. Firstly, the mitzvah of teshuva is perennial, not seasonal. Rabbeinu Yona opens Sha'arei Teshuva by underscoring the vital obligation to repent immediately, as soon as one becomes aware of cheit. Likewise, Maharsha comments that when Chazal detail the mitzvah of studying the appropriate seasonal halachos on the respective yomin tovim (halachos of Pesach on Pesach, Shavuos on Shavuos, Sukkos on Sukkos) they conspicuously omit mention of Rosh Hashanah and Yom Kippur, lest one erroneously think that mitzvas teshuva is seasonal and limited to the Yomim Noraim.
Secondly, the exclusive association of teshuva with din yields a truncated, distorted view and vision of teshuva. The goal of teshuva becomes settling accounts, attaining forgiveness and winning a favorable verdict. Completely absent from that vision is change. The mitzvah of teshuva actually entails affecting formidable, even dramatic personal change - transforming our character and very persona.
צריך לחפש בדעות רעות שיש לו ולשוב מהן
one has to identify his bad character traits and repent from them
מן הכעס ומן האיבה ומן הקנאה וכו'
from anger and enmity and jealousy etc. ...
ומן רדיפת הממון והכבוד ומרדיפת המאכלות וכו'
from pursuit of money, honor and food...
(Teshuva, 7:3)
משנה שמו, כלומר אני אחר ואיני אותו האיש שעשה אותן המעשים
he changes his name, so as to say that I am different; I am not the same person who committed those [sins]
(Teshuva, 2:4)