Is the prayer of someone who watches pornography after repeated repentance and just before repentance valid and accepted, and does Allah punish the doer of that by cutting off provision, and what is the way to sincere repentance?

Obedience to Allah, His remembrance, and the recitation of the Quran bring fear and awe to the heart. Let the servant be truthful with Allah, so that Allah may make hateful to him what Satan has beautified of sins. Let him strive against his self in prayer to repel intrusive thoughts, and let him seek refuge from Satan and spit to his left three times if they return. His prayer is valid and not nullified by these thoughts. Sins and transgressions are a cause for the removal of blessings, and the preservation of blessings is achieved through obedience to Allah and gratitude to Him, in affirmation of His saying, the Almighty: "And [remember] when your Lord proclaimed: 'If you are grateful, I will surely increase you [in favor]; but if you deny, indeed, My punishment is severe.'"