Verily, Allah Almighty extends His Hand during the night so the sinner of the day may repent, and He extends His Hand during the day so the sinner of the night may repent until the sun rises from its west

The acceptance of repentance will continue as long as its door is open, and its door will be shut when the sun rises from the west, and as long as one repents before the death rattle, i.e., when the soul reaches the throat.
One's sin should not lead him to be desperate and hopeless because Allah's pardon and mercy are vast and the door of repentance is open.
Conditions of repentance: First: To abandon the sin. Second: To regret doing it. Third: To be determined not to return to it ever. This applies in case the sin has to do with the rights of Allah Almighty; however, if it is related to others' rights, then a condition of the validity of the repentance is to restore the right to its owner or the one to whom the right is due forgives him.