Dua for Day and Night

The most superior way of asking for forgiveness from Allah is to recite:
اللَّهُمَّ أَنْتَ رَبِّي لّا إِلَهَ إِلَّا أَنْتَ، خَلَقْتَنِي وَأَنَا عَبْدُكَ، وَأَنَا عَلَى عَهْدِكَ وَوَعْدِكَ مَا اسْتَطَعْتَ، أَعُوذُ بِكَ مِنْ شَرِّ مَا صَنَعْتَ، أَبُوءُ لَكَ بِنِعْمَتِكَ عَلَيَّ، وَأَبُوءُ بِذَنْبِي فَاغْفِر لِي فَإِنَّهُ لَا يَغْفِرُ الذُّنُوبَ إِلَّا أَنْتَ
Alahumma anta rebi la ilaha ila ant, khalacktanee, waana abduk, wa ana ala ahdick wa wahdick mstata-ht, authu bika min shree ma sana-ht, aboouh laka bi ni'mateeka aley, wa aboouh bi thenbee faghfirlee fa inawho la yeghfr uthunooba illa ant.'
(O Allah, You are my Lord. None has the right to be worshipped but You. You created me and I am Your slave. I am faithful in my covenant and my promise (to You) as much as I can. I seek refuge in You from all the evil I have done. I acknowledge before You all the blessings You have bestowed upon me, and I confess to You all my sins. So I entreat You to forgive my sins, for nobody can forgive sins except You.)
The Prophet (S) added that if somebody recites it during the day with firm faith in it, and dies on the same day before the evening, he will be one of the people of Paradise. And if somebody recites it at night with firm faith in it, and dies before the morning, he will be one of the people of Paradise