The supplication of Yoonus (Jonah) is one of those narrated on the authority of the Messenger of Allah which was answered from Allah The Almighty. The Messenger of Allah said: "As for the supplication of Thun-Noon (Yoonus), therewith he supplicated Allah while being inside the fish, ‘There is no deity except You; exalted You Are. Indeed, I have been of the wrongdoers.’ No Muslim supplicates Allah with it in anything, but Allah responds to him." [At-Tirmithi]
The Prophet said in another narration: "'Should I not teach you something; if anyone supplicates Allah therewith whenever he is stricken by distress or an adversity of this world, he will be guided to a way out of it?’ It was said, ‘Yes (tell us).’ He said: ‘It is the supplication of Thun-Noon.'" [Al-Haakim and An-Nasaa’i]
Allah The Almighty has opened for you this gate of response to supplication, in order to rectify your states. If you have learned about the Quran, supplication, Thikr (remembrance of Allah The Almighty), standing (in prayer), fasting and your heart has not yet responded to them, know that your inclination and worldly fortune have hindered you from hastening to compete in the race to realize them, perchance you would attain the forgiveness of Allah The Almighty. If you have reached such a state and despaired of rectifying your own self with what you have learned, and instead find it too difficult for you to do, and find obstacles impeding you from performing acts of worship: then, that is the way you can get rid of such despair and difficulties.
It is most likely that this supplication, with the etiquette mentioned above, will be a means of eliminating distress, resolving the problems we are suffering from, and removing the adversity that has afflicted us, as mentioned by the Messenger of Allah . It is incumbent upon one to hasten to Allah The Almighty, sparing no time and no effort, and be in the best state in which his supplication may be accepted by Allah The Almighty. If his supplication is accepted, our conditions will become rectified, both the soul and heart will hasten to respond to those deeds and acts of worship and the breast will be expanded (to the truth). In this way one's feet will be firmly established on the way to Allah The Almighty, receiving light to their Lord, mercy will descend and our misery will be removed. Consequently, the man whose supplication is answered will have his gates opened for him, i.e. the gates of healing and guidance, mercy and response in compliance with His Saying (what means): {And your Lord Says, "Call upon Me; I will respond to you." Indeed, those who disdain My worship will enter Hell [rendered] contemptible.} [Quran 40:60]
A believer should do his best to avoid despair and enter upon Allah The Almighty. This will aid him in achieving what he has not obtained, keep him firm on what he has received, and receive much more of the mercy of Allah The Almighty in realization of the Statement of Allah (what means): {If you are grateful, I will surely increase you [in favor].} [Quran 14:7]
If you were certain that your supplication (by day while fasting), and at night (while standing in prayer), would surely receive an answer (from Allah The Almighty), then, with which supplication would one supplicate his Lord?
Undoubtedly, you would like your Lord to boost your faith, strengthen your determination, aid you in remembering Him, give thanks to Him, and worship Him in a sound manner of worship. You would like Him to expand your breast with the Quran so that you would approach it, draw closer to Him, help you in your occupation, avert evil from you and save you from (the evil of) Satan, the whispers of your Self and evil inclinations. By means of supplicating him sincerely, you will achieve many other blessings in your property, children, soul, work and morals, in the matters between you and Allah The Almighty, and in your dealings with people. This will remove adversity from you as well as from the Muslims. Ramadan is the season when those supplications are opened, and they are never rejected by day or night.