The following is adapted from the words of Rabeinu Yonah in Yesod Hateshuva:
A person who fell and wants to return to Hashem, let me teach you the correct way. On that very day he should throw away all his wrongdoings, and pretend as if he was born that day and he has no merits and no faults. Today is the beginning of his deeds. Today he will examine his actions so that they will not veer from the correct path. This tactic will bring him to return fully to Hashem. For he will imagine himself as if he's getting rid of his heavy load of wrongdoings. And his conscience will not disturb him from returning due to embarrassment from his wrongdoings, which may cause him to think, "How can I dare and return to Hashem when I sinned so terribly, I did such and such, I transgressed again and again countless times. I am embarrased to stand before Hashem - I feel like a thief who was caught red-handed. So how can I enter His court and do His mitzvos?" One must not think like that! Beacuse the YH sits like a fly at the doors of the heart, with new tactics each day, looking forward to trip the person, and he makes him think such terrible ideas. Rather, one must realize that this is Hashem's way, His hand is out-stretched to receive those who return. Therefore it is rightful that one should simply throw away his wrongdoings and make himself a new heart...
(If anyone relates to such chizzuk, feel free to read the rest of the holy words in the source.)
Hatzlacha
MT