Believe that Allāh [Glorified and Exalted be He] is Most Forgiving, Most Merciful! Allāh [Glorified and Exalted be He] says in the Holy Qur’an over and over again that He is All-Forgiving and Most Compassionate. How can you then lose faith in Allāh’s [Glorified and Exalted be He] mercy? Don’t forget the special Dua for the Night of Decree: اَللَّهُمَّ اِنَّكَ عَفُوٌّ تُـحِبُّ الْعَفْوَ فَاعْفُ عَنِّي O Allāh, You are Most Forgiving, and You love forgiveness, so forgive me.
Abu Dharr (May Allah be pleased with him) reported: The Messenger of Allah (ﷺ) said to me, "Shall I tell you the expression that is most loved by Allah?" It is 'Subhan-Allahi wa bihamdihi' (Allah is free from imperfection and His is the praise)'." [Muslim].reference : Book 16, Hadith 5 Arabic/English book reference : Book 16, Hadith 1412