Why does the questioner feel lost, frustrated, and unbenefited by acts of worship, despite observing the obligatory prayers, supererogatory prayers, and night vigil? Is this from the whisperings of Satan, and what is the reason for his cessation of memorizing the Qur'an?

Beware of abandoning worship, claiming it is not beneficial, for it is beneficial for the rectification of your heart, your worldly life, and your afterlife. Continue in obedience, increase in supererogatory acts, and be sincere in your acts of worship. Perform prayer with humility and presence. Strive in supplication for Allah to let you taste the sweetness of worship, and know that this is attained through struggle and perseverance. Accompany good people, adhere to gatherings of knowledge, and seek refuge in Allah from Satan. Do not neglect your worldly studies and bring to mind good intentions, such as benefiting Muslims and honoring your parents.