I read that same book and while I liked the overall message, I really found factors of happiness to be too limiting. His sample set also, is a paltry 1500-1800 people if I recall. I am an introvert and I love spending time alone, reading, playing video games, watching "how-to" programs, etc. I remember him listing hobbies that "unhappy retirees" partake in as reading, fishing, and other solitary things. I say rubbish! The key is, sprinkling in some meaningful social interaction ALONG with your solitary pursuits. The greatest thing about being FIRE'd is really the plethora of options. I wouldn't worry about happiness, it will surely follow you into FIRE!