What should one do if afflicted by obsessive doubts about polytheism (shirk) in words and deeds, to the extent that it prevents them from eating or sleeping and causes them to lose the desire to live? Is there a cure for this?

"Curing obsessive whisperings (waswasah) requires determination, perseverance, and patience. It combines three matters: turning away from the obsessive whisperings, frequently seeking refuge and supplicating to Allah Almighty through prayer (du'a), and increasing good deeds such as remembrance (adhkar), reading the Quran, and prayer (salat). It is also advised to avoid isolation and idleness and to be keen on righteous companionship. And know that this tribulation elevates your ranks and multiplies your good deeds, and your dislike for it is a sign of the soundness of faith in your heart."