gnaw at
phr. v..phr. v.. to make you feel worried or unhappy for a long time.
phr. v.. to cause persistent distress or anxiety; figuratively, to erode one's peace of mind through constant, repetitive worry.
The secret began to gnaw at him.
Even though she apologized, the guilt continued to gnaw at her for weeks.
The suspicion that he had been betrayed began to gnaw at his confidence, eventually undermining his ability to lead the team effectively.
usually takes an abstract noun like guilt, doubt, or worry as the subject or object.
connect the figurative meaning to the literal action of a rodent chewing on something; this visual helps students understand the 'slow erosion' of one's mood.
The doubt gnawed him.The doubt gnawed at him.the preposition 'at' is essential to indicate the persistent, repetitive nature of the feeling.