Hadith:

Asmaa' bint Omays, radi Allahu 'anha, said: Allah's Messenger,sal Allahu alayhi wa sallam, told me, "Shall I not teach you words to say whenever you are aflicted with something? Say:'Allahu Rabbi (Allah is my Lord), Laa Shareeka lah (He has nopartner).'" - Abu Dawood

[Lessons from this hadith] :

The entire universe is the creationof Allah. When you find yourself aflicted by something, followthis advice of what to say and notice what happens. Allahurabbi, laa shareeka lah!