Answered by Sayyidi Habib Umar bin Hafiz (may Allah protect him and benefit us by him).
I am in great difficulty. What dhikr should I recite?
You should turn yourself to Allah and repeat the Prayer of Difficulty [Dua al-Karb] which the Best of Creation ﷺ taught us:
لاَ إِلَهَ إِلَّا اللهُ العَظِيمُ الْحَلِيم
لاَ إِلَهَ إِلَّا اللهُ رَبُّ العَرْشِ العَظِيم
لاَ إِلَهَ إِلَّا اللهُ رَبُّ السَّمَاوَات وَرَبُّ الأَرْض، وَرَبُّ العَرْشِ الكَرِيم
La ilaha ill-Allah ul-`Azimul-Halīm,
La ilaha ill-Allahu rabbu’l`arshi-l’`azim,
La ilaha ill-Allahu rabbu`ssamawati wa rabbu’l-ardi wa rabbu’l`arshi-l-karim
“There is no god but Allah, the Awesome, the Forbearing, there is no god but Allah, the Lord of the mighty throne, there is no god but Allah, the Lord of the heavens and the earth and the noble throne.”
Also repeat abundantly:
يا حَيُّ يا قَيُّوم
Ya Hayyu Ya Qayyum
O Living! O Sustainer!
Also bestow abundant prayers upon the Prophet (may Allah bless him and grant him peace).
In one instant Allah can change someone’s state. May Allah remove all difficulties from all of us, by Your Mercy, O Most Merciful.