When in any difficult

اللَّهُمَّ رَحْمَتَكَ أَرْجُو فَلَا تَكِلْنِي إِلَى نَفْسِي طَرْفَةَ عَيْنٍ وَأَصْلِحْ شَأْنِي كُلَّهُ لَا إِلَهَ إِلَّا أَنْتَ

“O Allah, I hope for Your mercy, do not leave me for even the duration of an eye blink (duration) and correct my total condition. Besides You there is none worthy of worship”.

(Hisnul Hasin)

حَسْبُنَا اللَّهُ وَنِعْمَ الْوَكِيلُ

“Allah is sufficient for us and He is the Best Guardian”.

(Quran, Surah Al-Imraan)

اللَّهُ اللَّهُ رَبِّي لَا أُشْرِكُ بِهِ شَيْئَاً

“Allah is my Lord, I do not ascribe anything unto Him”.

(Hisnul Hasin from Abu Dawood)

يَا حَيُّ يَا قَيُّومُ بِرَحْمَتِكَ أَسْتَغِيثُ

“O Alive and everlasting One, I beseech You by Your mercy”.

(Mustadrak Hakim)

لَا إِلَهَ إِلَّا أَنْتَ سُبْحَانَكَ إِنِّي كُنْتُ مِنَ الظَّالِمِينَ

“O Allah, there is none worthy of worship besides You. You are Pure, definitely I have oppressed my soul by sinning”.
The Qur’an states that these words were recited when Yunus (A.S.) called upon Allah from the belly of the fish. Prophet Mohammad (S.A.W.) stated in a hadith that when any Muslim makes this dua via these words to Allah, then Allah surely accepts his duas.

(Tirmidhi etc)