Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: When the Prophet (peace and blessings be upon him) prayed, after finishing the prayer he would place his right hand on his head and recite:
'Bismillahil-ladhi la ilaha illa huwar-rahmanur-rahim, Allahumma adhhib 'annil-hamma wal-hazan'
"In the name of Allah Almighty, seeking blessing, besides whom there is no deity; He is the Most Gracious, the Most Merciful. O Allah, remove anxiety and grief from me."
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأذكار / 16971