A trigger is something that causes a negative emotion, and in eating disorder recovery, a trigger can sometimes cause an individual to resume disordered eating or exercise behaviors. The best way to deal with triggers in anorexia recovery is to work with a therapist to identify your triggers and learn healthy coping mechanisms to practice instead.
For example, perhaps seeing a social media post about dieting or weight loss makes you feel like you should start restricting your food intake again. Rather than engaging with this thought, try to find a way to cope, like using a deep breathing exercise or calling a loved one.