What’s a book that helped you get through to the other side of a bad mental health period?

I'm looking for any book in any genre (fiction or non fiction) that helped you through a slump or particularly low period of mental health? Feeling pretty anxious all the time and want to change my perspective on it. Kinda goofy but a million years ago when I was 12 experiencing my first wave of existential depression, twilight helped me realize that mortality is ok. I was like "no sleep? High school forever? Living forever? No thanks life is fine with an experation date". You never know what's going to change the way you think when you're goin through a rough time. What books helped you all?