I don't usually read general self-help books - I look for books on specific topics.
One book that is maybe appropriate for Post-FIRE is Younger Next Year: Live Strong, Fit, and Sexy - Until You're 80 and Beyond by Chris Crowley.
"This book tells how to put off 70% of the normal problems of aging (weakness, sore joints, bad balance) and eliminate 50% of serious illness and injury.The key to the program is found in Harry's Rules: Exercise six days a week. Don't eat crap. Connect and commit to others. There are seven rules all together, based on the latest findings in cell physiology, evolutionary biology, anthropology, and experimental psychology."
Lots of excellent and fairly badass advice.