What should someone do who is afflicted with masturbation, and Satan beautifies its practice to him by associating it with God, and he feels despair of repentance and sees himself as an infidel?

Satan drags the servant towards evil step by step until he reaches indecencies and disbelief. The servant must offer sincere repentance and distance himself from masturbation and malicious thoughts, and beware of Satan's enticement. He should marry if he is able, or fast if he is not able, as it curbs lust. He must keep himself chaste and occupy his time with studying or beneficial sports, and frequently read books of encouragement and deterrence, and remember the horrors of the Day of Judgment. Allah accepts the repentance of His repenting servants and forgives their sins.