Recite this when a grevious matter occurs in your heart

Jameel bin Darraj said to Imam Abu Abdillah (as): There has occurred in my heart, a grievous matter [which is disturbing me].
So Imam (as) said: Say: There is no God but Allah (لا إله إلا الله).
Jameel bin Darraj said: So every time something occurred in my heart, I’d  say: There is no God but Allah, and it would go away from me.

al Kafi, Volume no. 2, Page no. 424