I was fairly stressed out! Giving up a well-paying job was scary, and deciding when to give notice was stressful, and I was anxious about how it would all turn out. I had a lot of feelings of guilt too, like I was letting people down by leaving.
Work itself was fine though. I was at the top of my game and I generally liked my job. I ended up FIREing gradually. First part time, and then *very* part time, and then no work at all. It took me quite a while to let go. I'd say 2 years of pre-FIRE anxiety, followed by a year of Post-FI emotional bumpiness, followed by mellow happiness.
SIS