Book about health (mental, physical, mindfulness) or A BOOK that changed your life ….new to reading

1. I was struggling with a few health issues and that got me into thinking about every foo choices, decisions etc that I was taking. If there are any book suggestions which could be considered like a holy grail for health: it could be physical health, mental health, food, daily life practices, mindfulness anything like that. Needs to be like a book that has been well researched before writing. If the author is a professional in that domain even better.
2. or you could recommed your favorite book, your no. 1 that changed your life for good. i don't mind if it's fiction but a book that really changed your life, gave you clarity and stuff, I am new to reading and would love to get some great recommendations
3. I also find myself living in the past a lot either regretting past decisions or constantly thinking about the best moments from earlier times. I know it’s not helpful, but it still happens. Are there any books that explore why we do this and how to break out of it, ideally in a thoughtful or psychologically grounded way?

thanks in advance 🙂