Why does the worshipper's mind wander during prayer, despite seeking refuge in God from Satan?

Forgetfulness and absentmindedness are part of human nature, and the Prophet, peace and blessings be upon him, used to be forgetful and absentminded. To overcome frequent absentmindedness in prayer, one must strive for devotion, presence of heart, and avoid preoccupation with worldly matters. When one feels the whispers of Satan (Khinzab), one should seek refuge in Allah from him and spit to the left three times, with sincerity, truthfulness of heart, and seeking Allah's help.