Du'a when needing strength

لَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللَّهِ

La hawla wala quwwata illa billah

There is no strength except in Allah.

Ṣaḥīḥ al-Bukhārī 6384, Ṣaḥīḥ Muslim 2704