What happened to Fitz that has caused him to have a difficult time remembering his past? How does he feel about his past?

He was mortally wounded by Regal, then he took poison to die. He was buried, and then revived by Burrich and Chade. To bring Fitz back to life, he was trusted to a wolf who had been bound to him. Fitz is thinking of his past, and he wonders if he should thank these men for bringing him back.