From the excellent book The Prophet of Mercy: Muhammad, Scenes from his life by Osman Nuri Topbas.
Prophet Muhammad (saws) had no sins. Yet he continued to pray at night until his feet were swollen and he continued to recite the Qur’an until he got exhausted. He loved, thanked, feared and remembered Allah more than anyone else.
Salat is the union of the servant with his Lord. It is going up to the divine presence. It is a source of endless pleasure for the lovers of Allah. They make voluntary worship with the purpose of maintaining the pleasure of worship.
There is submission in the salat. This is the reason why the ego dislikes it. Only this characteristic is sufficient to show that Islam is a true religion and that salat is the highest form of worship.
Those who are overcome by their ego, do not come close to salat while those who cannot pass the obstacle of their ego stick to the form of salat. The real salat is a blessing given to only a few people.
The Messenger of Allah expressed this truth as follows:
“Two people may make salat in the same place but the difference between them is like the difference between the earth and the sky.” (Musnad al-Shashi)