In the Name of Allaah, the Entirely Merciful, the Especially Merciful.
…Allah has opened the gate of repentance to the one who wants to turn back from his sin and wants to repent and seek forgiveness. He should not despair of the pardon and forgiveness of Allah. That is what the shaytan (devil) wants from the sinner and apostate. Yes, he should feel regret for his sin, but it should not become a barrier between him and Allah that prevents him from repenting and seeking forgiveness.
Allah says (interpretation of the meaning):
“Say: O ‘Ibadi (My slaves) who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allah, verily, Allah forgives all sins. Truly, He is Oft‑Forgiving, Most Merciful.” [39:53]
It was narrated from Abu Moosa (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “Allah holds out His hand at night to accept the repentance of those who have sinned during the day, and He holds out his hand by day to accept the repentance of those who have sinned at night – until the sun rises from its place of setting.”
Ibn Rajab al-Hanbali (may Allah have mercy on him) said:
It was said to al-Hasan al-Basri: One of us feels too shy before his Lord to ask forgiveness for his sin then go back to it, then ask forgiveness then go back (to his sin)? He said: The shaytan wishes that he could achieve that with you. Do not tire of seeking forgiveness.
And it was narrated that he said: I think that this is the attitude of the believers – i.e., every time a believer sins, he repents.
Jami’ al-‘Uloom wa’l-Hikam.
[REF: IslamQA.info – 91408]