«كان إذا كربه أمر قال: يا حي يا قيوم برحمتك أستغيث»
It was the practice of the Prophet (peace and blessings be upon him):
"When some matter distressed him (peace and blessings be upon him), he (peace and blessings be upon him) would say: O Ever-Living, O Sustainer of all! In Your mercy I seek relief."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4777