The Prophet (SallAllahu Alyhi wasallam) said to his companions: 

"Shall I not tell you some words which, if distress or grief befalls any of you and he makes this du'aa, it will bring him joy? It is the du‘aa’ of Dhoo’l-Noon (i.e. Yunus):

لاَ إِلَهَ إِلَّا أنْـت سُـبْحانَكَ إِنِّي كُنْـتُ مِنَ الظّـالِميـن

‘Laa ilaaha illa Anta, subhaanaka inni kuntu min al-zaalimeen.
 
‘There is no god but You, Glory to You; verily I was one of the wrongdoers.’" 

 
(Saheeh al-Jaami‘, no. 2605).