I would really like to know about Sayyiduna Muhammad what is the Du'a that everyday he had to say and loved to say, and that helped him through everything everyday?
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The Prophet used to supplicate Allah during the day and night by many different supplications, in which he asked Allah for something and sought protection from some other things. Some of the supplications are mentioned here.
1- "Ya hayyo yaa qayyoom, birahmatikaa astagheeth, aslih lee sh'anee kullah, walaa takilnee ilaa nafsee tarfata 'Aayn." [At Tirmithi]
(O Ever Living, O Self-Subsisting and Supporter of all, by Your mercy I seek assistance, rectify for me all of my affairs and do not leave me to rely on myself, even for the blink of an eye).
2- "Allahumma innee as-alukal-'Afwa wal-'Aafiyah, fid-dunyaa wal-aakhirah, allaahumma innee as-alukal-'Aafwa wal-'Aafiyah fee deenee, wadunyaya wa ahlee, wa malee, allaahummastur 'Aawraatee, wa aamin raw'aatee, allaahummah-fathnee min bayni yadayya, wamin khalfee, wa'aan yameenee, wa'aan shimalee, wamin fawqee, wa-A'aoothu bi'aathamatika an ughtala min tahtee." [Abu Daawood]
(O Allah, I ask You for pardon and well-being in this life and the next. O Allah, I ask You for pardon and well-being in my religious and worldly affairs, and my family and my wealth. O Allah, veil my weaknesses and set at ease my dismay. O Allah, preserve me from the front and from behind and on my right and on my left and from above, and I take refuge with You lest I be swallowed up by the earth).
Ibn 'Umar said: "The Prophet never gave up supplicating these supplications in evening and in morning."
3- "Allahumma 'Aafinee fee badanee, allaahumma 'Aafinee fee sam'Aee, allaahumma 'Aafinee fee basaree, la ilaha illa ant. Allahumma innee A'aoothu bika minal-kufri, walfaqri, allaahumma innee A'aoothu bika min A'athabil-qabr." (Three times in morning and in evening).[Abu Daawood]
(O Allah, grant my body health, O Allah, grant my hearing health, O Allah, grant my sight health. None has the right to be worshipped except You. O Allah, I take refuge with You from disbelief and poverty, and O Allah I take refuge with You from the punishment of the grave. None has the right to be worshipped except You. O Allah, I take refuge with You from disbelief and poverty, and I take refuge with You from the punishment of the grave. None has the right to be worshipped except You) (Three times).
We advise the questioner to refer to the books or supplications to know more supplications that were recited by the Prophet at morning and evening.
'Hisn al-Muslim' written by Shaykh Sa'eed Al-Qahtaani, may Allah preserve him, is a short and authentic book on this subject. It is translated in English also; we advise you to own this book.
Allah Knows best.