How can one stop watching forbidden films, given the repeated repentance and relapse, and the fear that repentance may not be accepted?

The door of repentance is open and will not close until the sun rises from the west. No matter how many times a sin is repeated, one must repent and return to Allah without despair, for Allah forgives as long as the servant seeks His forgiveness. One must strive against their soul to rid themselves of sin by seeking Allah's remembrance and supplication, reflecting on His names and attributes, being mindful of His omnipresence, remembering death and the horrors that follow it, and associating with the righteous. This is a sincere struggle accompanied by trust in Allah and having a good opinion of Him, for whoever strives for His sake, He will guide them to His paths. If the sin is repeated, then repent and continue repenting until Allah bestows the complete abandonment of the disobedience.