Our master Shahr bin Jaushab (Allah be pleased with him) says:

“I asked Umme Salma (The Mother of the Believers, Allah be pleased with her) ‘What was the supplication (dua) most often made by the Prophet of Allah (blessings and peace of Allah be upon him) in his house?’

She replied that Prophet of Allah (blessings and peace of Allah be upon him) used to recite,

يَا مُقَلِّبَ الْقُلُوْب ثَبِّتْ قَلْبِىْ عَلٰى دِيْنِكَ

O the Controller of hearts! Make my heart firm on Your Deen.

(Tirmizi)