Should one act upon assumption if one forgets whether one washed one's hands after impurity, given that one leans towards having washed them, and what is the precise meaning of "preponderance of assumption"?

Summary of the Answer: A person who experiences frequent doubts should not pay attention to them, but rather disregard them, based on the statement of Ibn Uthaymeen: "And doubt after an action has no effect... and similarly, when doubts become frequent." Therefore, doubt must be ignored if it reaches the point of frequency or repeated forgetfulness, whether there is a predominant assumption or not. The difference between doubt (shakk) and predominant assumption (ghalabat al-dhann) is that doubt is the equality of two possibilities, while predominant assumption is the favoring of one of the two possibilities.