Great question!
When we "retired" we honestly didn't think about it too much. In our mind, we had plenty of money and our main goal was to stay home with our future child. MMM started a new business (which cost us a lot of money, so that was definitely stressful!), but the leaving work part was very easy.
And, as MMM mentioned, you end up working anyway. After we had our son, I started doing bits of work here and there, MMM worked on construction jobs, and now that our son is in school, we have more time to work or do other things.
In fact, we recently met a retired man down the street who just moved to our town. He was out clipping flowers and we asked him if he did gardening work. He told us he was retired, had sold his car and biked around town, and spent most of his time hanging out on a patio of a local eatery. But, somehow word had gotten out that he was good with gardens and all of a sudden he was picking up all this work.
This example is exactly how things seem to us. I turn down real estate work all the time, but word still seems to get around that I'm a realtor and people keep asking me for their help.
So, financially, I think the trick is to have a low cost of living and have some skills. Paying off your house and having low monthly payments is obviously ideal. If times get tough, you can pick up a few jobs to get by, but you wouldn't need full time work to cover your minimal expenses.
Socially, that's an interesting question... we've never had this problem. We still go out to dinner with friends (we just order appropriately from the menu) and it seems like the majority of our friends have kids now, so we tend to just hang out at each other's houses. I don't know how old you are, but as you get older, it seems that many of us prefer lower cost activities. You might find that your part-time gig can help pay for these activities too. I went to Vegas with the girls, MMM went on a fancy snowboarding trip, we travel every winter and visit Canada every summer, plus I'm paying a monthly fee for crossfit. Yet, our expenses are STILL about $20-24K per year. Also, you can have events and invite YOUR friends! BBQ and campfire in the backyard - people love that! And, go do the expensive things, but do them infrequently and maybe even do them differently. I can't imagine any outing where you can't control your own costs without alienating your friends.
So, I guess my question to you is... do you know what you might do in retirement? Do you have anything you're interested in pursuing? I didn't know what that might be, but it ended up being real estate for now. Later, I might try becoming a personal trainer. Maybe I'll work on community gardens or volunteer with trail building efforts and learn some skills there. Maybe I could help kids learn to read. Things always seem to change and I enjoy trying new things. Being FI gives you the ability to discover all these things about yourself!
Phewf! That was long, sorry! Let me know what you think! (and don't think so much). :)
