For me, it is not the usual fears of “I'll be bored”, “I'll be lonely”, “I have to be productive”, or “I might not have enough money”.
My fear is time. That the rest of my life, will pass too quickly. Weekends and vacation time passes so quickly. It's part cliche, part comic meme, and unfortunately, it is also the absolute truth.
So what is time like after being FIRE for a year or more? Do the days, weeks, and months seem to pass far more quickly then when you were grinding away at your job? Or is time more normal when you don't have to worry about going back to work on Monday, or when your vacation ends?