Do you pray for your heart? 
The Prophet ﷺ said, لَا يَسْتَقِيمُ إِيمَانُ عَبْدٍ حَتَّى يَسْتَقِيمَ قَلْبُهُ
“The faith of the slave cannot be correct until his heart is correct” [Musnad Ahmad: 13071]
Ask Allah:
1. To guide your heart:
اللَّهُمَّ اهْدِ قَلْبِي وَسَدِّدْ لِسَانِي وَاسْلُلْ سَخِيمَةَ قَلْبِي
O Allah guide my heart, correct my tongue and remove the spite of my heart. [Musnad Ahmad: 1997]
2. To fill it with light:
اللَّهُمَّ اجْعَلْ فِي قَلْبِي نُورًا
O Allah make light in my heart. [Sahih Bukhari: 6316]
3. To make it firm:
يَا مُقَلِّبَ الْقُلُوبِ ثَبِّتْ قَلْبِي عَلَى دِينِكَ
O Allah, the Turner of the hearts, make my heart firm on Your religion. [Jami` at-Tirmidhi: 3522]
4. To cleanse it:
اللَّهُمَّ اغْسِلْ قَلْبِي بِمَاءِ الثَّلْجِ وَالْبَرَدِ وَنَقِّ قَلْبِي مِنَ الْخَطَايَا كَمَا نَقَّيْتَ الثَّوْبَ الْأَبْيَضَ مِنَ الدَّنَسِ
O Allah! Wash my heart with the water of snow and hail, and cleanse my heart from all sins as a white garment is cleansed from filth. [Sahih Bukhari: 6368]
5. To protect it:
رَبَّنَا لَا تُزِغْ قُلُوبَنَا بَعْدَ إِذْ هَدَيْتَنَا وَهَبْ لَنَا مِن لَّدُنكَ رَحْمَةً إِنَّكَ أَنتَ الْوَهَّابُ
Our Lord, let not our hearts deviate after You have guided us and grant us from Yourself mercy. Indeed, You are the Bestower. [Surat Aali Imran: 8]
6. To make it sound:
وَأَسْأَلُكَ قَلْبًا سَلِيمًا وَلِسَانًا صَادِقًا
And I ask You for a sound heart and a truthful tongue. [Sunan an-Nasa’i: 1304]
7. To cool it:
اللَّهُمَّ بَرِّدْ قَلْبِي بِالثَّلْجِ وَالْبَرَدِ وَالْمَاءِ الْبَارِدِ اللَّهُمَّ نَقِّ قَلْبِي مِنَ الْخَطَايَا كَمَا نَقَّيْتَ الثَّوْبَ الأَبْيَضَ مِنَ الدَّنَسِ
O Allah, cool my heart with snow, hail and cold water. O Allah, cleanse my heart of sins as You cleanse a white garment of filth. [Jami` at-Tirmidhi: 3547]
8. To adorn it:
اللَّهُمَّ حَبِّبْ إِلَيْنَا الْإِيمَانَ وَزَيِّنْهُ فِي قُلُوبِنَا
O Allah, make us love belief and adorn our hearts with it. [Al-Adab Al-Mufrad: 699]