The aforementioned empowering words of the Ohr Hachaim Hakadosh could be put well to use with regard to our avodah of Teshuvah during the month of Elul. While the ideal way to do Teshuvah would be by maintaining a strict regimen of intense fasting; agonizing oneself physically and emotionally. Nowadays, however, due to ירידת הדורות (a generational weakening in Ruchniyus), we are unable to tolerate such a rigorous procedure, both spiritually and physically. Yet, whichever route we follow, we could merit a complete Teshuvah and have our sins totally forgiven, so long as we invest our utmost to better his ways, as is seen from the following words of the Benei Yisaschar.
The בני יששכר quotes the Arizal who said that within the word תשובה lies the actual methods of repenting. The first letter, Tav (ת), stands for תענית, fasting. The subsequent letters Shin (ש) and Vav (ו), are in reference to שק ואפר, the sackcloth and ashes customarily worn over one's body and head, respectively, as a sign of grieving. Finally, the last two letters Beis (ב) and Hei (ה), allude to בכי' והספד, wailing and mourning. However, the Bnei Yisaschar then quotes the Chida who says that only in the past could one demand such intense effort in order to achieve a complete teshuvah.
Nowadays, however, due to ירידת הדורות, we cannot demand such a high level of Avodah from people. Nevertheless, even we, with our limited physical and emotional strength, could merit complete atonement for our sins through following a more sustainable and attainable approach. This approach is also hinted in the word teshuvah which is an acronym for תורה, devoting more time for Torah study, שבת, being meticulous to keep Shabbos properly, וידוי, confessing to one's sins, בושה, shame and הכנעה, being humble and submissive to the will of Hashem (בני יששכר מאמרי חודש תשרי מאמר ד' דרוש י"א אות ל"ו).
Perhaps the reasoning behind this is as follows: The word "תשובה" means to return. When doing Teshuvah, we seek to mend our ways and return to the Straight path which leads closer to Hashem; whichever method will do so. Through our sins we have become distanced from Hashem, and by doing Teshuvah we once again come closer to Him. Of course, as noted above, we must do all that we could to merit atonement for our sins.. Only then, will we succeed in overcoming all obstacles that stand in our way, as the אור החיים הקדוש promises. Ideally, though, one should choose the method sustainable for him, as the pasuk says; "בתחבולות תעשה לך מלחמה" - with strategy shall you wage war (משלי כ"ד, ו'). In combat one would only use the most effective tactics, so too when doing Teshuvah, one shall pick out the most effective approach.