What should one do who suffers from frequent doubts during prayer, and should one continue to ignore them as long as the cure of devotion has not yet been achieved?

If a worshipper experiences doubt every day, even if only once, then it is a pervasive doubt (shakk mustankah) that should be disregarded. The person should proceed in their prayer based on what they are most certain of. However, if the doubt occurs one day and is absent another day, then it is not a pervasive doubt, and the ruling is that it must be cast aside and ignored, building upon the lesser of the two possibilities, along with performing the prostration of forgetfulness (sujood al-sahw).