Does Allah Almighty's saying: "Nor is there any hardship on the sick" apply to the person afflicted with obsessive-compulsive disorder who might omit a pillar or an obligatory act in prayer due to his delusion, trying to ignore that so that Satan does not gain control over him?

If a person suffering from waswasah (obsessive doubt) becomes certain that they have omitted a pillar or a duty, they must make up for the deficiency, like anyone else. However, if the matter is merely an illusion or a doubt, then it is obligatory for them to completely disregard these obsessive whispers, because giving in to them increases the act of worship [unnecessarily] and opens doors to evil. The cure for waswasah is to turn away from it and pay no attention to it. The person afflicted with waswasah should hold firm to the truth and repel whatever opposes it from the whispers of waswasah. Jurists have stipulated that excessive doubt, which becomes like waswasah, should be dismissed and not given any attention, because doing so leads to an increase in prayer [unnecessarily]. This is from Allah’s alleviation and mercy upon His servants, as He has removed hardship from them, for He does not burden a soul beyond its capacity. The verse, "And there is no hardship upon the sick," includes the person afflicted with waswasah because they are sick. They are commanded to fear Allah to the best of their ability and are not held accountable for what they are unable to do.