I usually have a lot of trouble sleeping and was panicking after I read the book. The side effects of not sleeping did seem kind of exaggerated, but glad to know someone actually took the time to corroborate all the claims.
Yes I write letters to my future self once in a while, maybe a year or two into the future. It's really interesting to read what my life was like when I wrote the letter and I'm always curious if things turned out as expected and if I managed to achieve some of my goals.