Final answer:
Mrs. Galley advises Steven to concentrate on areas within his control, suggesting a positive and proactive approach to dealing with challenges instead of dwelling on unchangeable circumstances.
Step-by-step explanation:
Mrs. Galley tells Steven not to agonize over things he can't change, but instead implies that he should focus on what he can influence and better manage his reactions and emotions. This advice is rooted in the philosophy of focusing on our internal attitudes and efforts rather than external circumstances beyond our control. The texts provided suggest a thematic approach to dealing with challenges and adversity, emphasizing the importance of self-control, the will to change, and taking proactive steps towards personal growth.