How do I write a letter to my friend telling him what you do to get good health?

How do I write a letter to my friend telling him what you do to get good health?

What makes you qualified to tell anyone what they must do to “get good health”? Are you a doctor? Nutritionist? A certified personal trainer?

Has this friend ASKED for your input on their health? If not, then why are you putting your nose into their business?

And why would you write to this person? If they’re a friend, why not just call or speak in person?