What is the reason for the lack of khushu' (devotion/humility) in prayer and acts of worship despite commitment and abstaining from prohibitions?

To achieve khushu' (devotional humility) in prayer, one must ponder the Qur'an, supplications (du'as), and remembrances (adhkar), and strive against one's self to attain it, knowing that it is the spirit of prayer and one of the greatest requisites for success. Khushu' is achieved by turning wholeheartedly to prayer, turning away from worldly matters, contemplating the meanings of the verses, avoiding everything that distracts the mind, and supplicating for its attainment.