FIRED since 2019. There have been plenty of times when I wished to be back in my industry. But, by now, I have figured out ways to keep myself busy. Mostly lots of times with my kids and lots and lots of sports. Every single school holiday we’re traveling etc. And active investing (unfortunately 
instead of passive) also covers some of my time.
FIRE or normal retirement, I get the impression that many don’t know what to do with the time they have when retired. So I would say, have a very clear plan on what you want to do with the extra time. If there is no clear answer to that, then I’d suggest part time. And if you have no idea what to do with your free time and actually love your job, then I’d continue and maybe run a little more risk in the job role, because the worst things that could happen would be to be fired into FIRE.
Also be clear about the expenses like AHV for non working residents. Kinda painful to pay AHV based on overall assets, pay income tax on fictional income (Eigenmietwert), etc. all while non receiving a paycheck.
EDIT: and yeah, if your social life centers around work or work related colleagues, acquaintances, friends… that will change and can lead to some loneliness. Need to find alternative ways- club memberships (Verein), volunteer work etc.