Interesting, and diverse discussion. Not surprisingly, everyone's retirement experience is different.
I am a month away from my 8 year FIRE anniversary. I retired 2 weeks before my 55th birthday. Some people ask me "how do you retire at 54?" and I reply, "You decide that is what you are going to do when you are 28, and live a life that will get you there.
DW retired 2.5 yrs ago and remarks to me often how amazing it is. We travel a LOT, and we travel well. Last winter we took our RV from New England to San Diego and back in 75 days (we hiked a total of 100 miles on that trip). We have a great, but fairly small, group of good friends and neighbors, some of whom are former co-workers.
I have never been busier. I lost 24 lbs in the first 8 months after being retired. Unintentionally. I though something was wrong ( I am a cancer survivor also). But it was just that I much more active, on my feet a good part of the day and am eating a little less junk food, and a LOT less food in quantity. It is rare for me to go to a restaurant and not take 1/2 of my entree home.
But nobody who knew me well ever asked me "what are you going to do?" after retiring. One of my former bosses said when I retired from 30.5 years in Medical Technology, "Yeah, work was always kind of an inconvenience for you, wasn't it?". He was right. I generally always liked my job, enjoyed the people I worked with, but it was never my passion or "my life". I used to get annoyed with the term "Work Life Balance". Like they are 2 different things. Isn't work part of your life?
I have never been busier. I have 3 antique cars, have run a hobby/business in the antique car hobby for over 20 years. I hike 500-600 miles a year, love cooking (and eating), and travel and going on other adventures with our good friend, most of whom now are also retired.
Happy? Yes, never been happier. 5+ years ago we bought a lake house as a second home, now we both live here full time. It is an amazing place. Our daughter lives an hour away and we see her most weekends. Enjoying what this retirement portfolio allows us to do is far beyond what I ever imagined it would be.