Great thread and responses! I've enjoyed reading this one.
I'm FI but not yet RE myself, but I did want to make mention here of the so called "Get a Life" tree from Ernie Zelinski's book 'How to Retire Happy, Wild and Free'. The book is redundant in a lot of places and might include a lot of obvious information if you're already deep into planning for and thinking about your FIRE'd life, but I'd still recommend it overall and picked up some good nuggets from it myself. This "Get a Life" tree idea was a big one.
Search images of this concept online, but basically you list out the following four "branches" of the tree:
1) the present ... what are the things I like to do right now that make me happy, are satisfying and fulfilling, just plain interesting, etc?
2) the past ... what are the things I used to like to do and might like to do again someday but I don't have the time for while working?
3) the future ... what are the things I'd like to do someday, am planning to do or have always been curious about and interested in? Could be long-term projects, shorter experiences, whatever.
4) things that will keep me physically active and fit
If I fill out my own list, it looks like this:
1) foreign language study, guitar
2) foreign language study (a different language, basically, one that I'd like to pick up again), piano, music composition and recording, amateur electronics tinkering, drawing/illustrating, knots (as in tying, memorizing different kinds and techniques), videogames.
3) almost everything in my #2 list above!, resume piano lessons, classes on more advanced drawing/illustrating, some videogames, hiking and long walks around my city, visiting and reading at the library, watch and re-watch loads of films, play in a band and maybe even record an EP for fun, compose for an amateur film, travel across the Atlantic as a passenger on a container ship, yoga, adopt a cat, take the time to develop close friends (something I never have any time for) ... and on and on!
4) weight lifting, biking, hiking/walking, yoga
What you end up with is basically a big list or menu of things you can choose from on any given day, so you really never have an excuse for being bored. There is always something small you can get into for a bit or a larger project to resume and attend to. If I take the list above and put it into a weekly schedule, that schedule is soon overflowing. The only thing that prevents me from pursuing these things is the enormous amount of time my work takes out of my waking hours. When I put that work time (and commute time and general prep time) into the same schedule, it's depressing how it just shuts everything else out. If I still found my work as fulfilling as I once did then it wouldn't bother me as much, but I'm so over it at this point.
Getting back to the "tree" above: definitely look at the images of this online, then sketch out your own. Let it sit a while, and I bet you'll keep coming up with new items to add to it, likely in the 'past' and 'future' sections. It's been an enjoyable exercise for me as I keep finding new items I'd forgotten about, or am reminded of something I'm very interested in for the future or would simply like to try and do. It makes me realize that the world outside of work is vast and goes out in all directions, and that thought helps greatly when I'm feeling overwhelmed at my job. It gives me back the perspective that this current work is just this one phase of my life.