Since we didn't "plan" for our retirement (serious illness, at the time, but with full recovery) no preparation per se... but recovery time was spent, creating literally dozens of large green spreadsheet, listing every conceivable situation for where we would (could, at the time) live, and what kind of lifestyle we wished for or might be able to afford.
Erring on the side of long term financial safety, we carved a possible pathway of frugality, but always with the hope of not having to return to the working world.
As a major consideration, even then, healthcare was a major concern (age 53, and with no company plan).
We planned possible details, different inflation rates, buying cars, major unforseen expense reserve plans, and varying life expectancies. Three months of working out different plans, with lots of homework in between. All of this because we didn't trust the Financial Advisor that we tried , who insisted that we needed an extra $200K, which would have meant many more years of saving back in1989. The group that he represented provided us with a glossy 20 page analysis of charts and math, so it meant taking apart the pieces and looking at our personal needs and wants.
Did all the planning work out as expected? Of course not, but when changes occurred, we were prepared to adjust, and over the long haul, arrived at the same goals, with no stress.
Luck maybe, but despite our original first 5 year plan to live in our campground home (park model on a lake), we spent the first 15 years being IL/FL snowbirds. Simple changes, like not buying the planned new cars, and skipping elaborate vacation plans, kept everything in balance. Buying IBonds when the limit was $60K/person/year, and the rates were relatively high in the early 2000's, kept us on a reasonable investment path, though not leading to wealth, avoided the mistakes that I knew I'd make if I tried on my own.
Probably luck, but FWIW, psychologically safe and we'd do it again.