I left my job with no future plans about a year ago. I was able to do this thanks to the company going through an IPO a few years prior and aggressive savings/investing in my 20's. I am 35 now.
What worked well for me:
1. Having a supportive partner. I am very lucky that my partner has not murdered me considering how much time we are at home together with her working all day from home and me not working. I know if roles were reversed, I would have a hard time.
2. Having existing hobbies that require time and discipline. Most of my hobbies are pretty cheap: running, reading, gaming, and cooking. The problem is, these all require time and discipline, which I used to not have. I treat my "hobbies" like a job and actually schedule time for each of these on a weekly basis. It's amazing how much time you can fill with stuff you love. It is also amazing how much more discipline you can have in your hobbies when you are not spending all of your "discipline points" on work. An exception for me is travel, which requires money, but not as much as you think if you fly on random weekdays and stay in hotels during off-peak times. Of course this has been limited during COVID.
3. Having some part time technical work. For me, this was taking on some advising and mentoring roles. I get paid for some of them, but mostly I do it because I enjoy it and I feel it keeps me connected enough to the rest of the technical world.
What did not work well:
1. Doing this during COVID. I was completely naive in thinking that we would be going through this for a "few more months" last year. Not being able to see family and friends was made even harder because I cut off my social connections from my work colleagues (I was lucky that I really liked most of my work colleagues). In hindsight, I wish I had thought through this more.
2. Alcohol consumption and other vices. Since I did not have to be up every morning at 7am anymore, I was staying up late and drinking ~5 nights a week. What got me to stop was my supportive partner identifying this for me and also seeing the liquor store bills add up. Thankfully, I was able to shake it, but it took about two months to change my habits.
3. Obsessing over the stock market. Since my assets are 90% tied to equities, I was obsessing daily over the green and red lines. This is somewhat common in a lot of FI/RE threads, but I realized that my very concentrated portfolio was stressing me out. I created a plan to slowly rebalance over the coming years, probably giving up some potential future gains, but the short term sanity gain is important to me.
Unexpected benefits:
1. Rarely waiting in lines. I can goto the bank or grocery store at 10:30am. I can goto a gym at 2pm. I still wonder why/how a lot of places are open during these hours, but I get to benefit from it.
2. Sleeping schedule fixed. While working, I was notorious for staying up late to get something done, sleeping 6-8 hours (which is pretty good), and feeling exhausted when I woke up. On weekends, I would rarely get up before noon because I was so tired. After stopping work, my sleep schedule has moved to a pretty fixed 10pm-6:30am and I no longer am a night owl. Nothing wrong with being a night owl, but I thought I was one for a long time, and turns out, I am not.
3. Exploring local area. With my limited vacation time, whenever we wanted to take time off, we would always hop on a plane and go somewhere. Having time and COVID restrictions had me exploring more locally (running trails, businesses, cafes, libraries). I have a much deeper appreciation for what local governments do to make the places we live more enjoyable.
Overall, I am very happy with the decision. I have no idea if I will end up going back to work or not. I realize that I am in the 0.0000001% of people that is lucky enough to be even thinking like this.