I don't post often, being a noobie to all this FIRE stuff, I've been eaten a live a couple of times, so I know how the OP feels LOL!
I just learned about the whole FIRE concept 2 years ago, but luckily I had the basics down for many years. Be as productive as possible (earn money), spend WAY less than you earn (be frugal), invest the rest (mostly stocks). My goal was to FIRE last May, with wife to follow in December (who was about as anti-FIRE as possible before we got married 4 years ago). COVID tweaked that a bit, we both got let go in August last year, but got to collect unemployment. In the meantime, we both ourselves up as Independent Contractors from home with minimal travel, and work 2-4 hours per day. Not 100% FIRE, but enough to get us out of the traditional rat race.
I can tell you that my first year of FIRE did not go as planned. Stock market up a lot, and I had a lot in cash as my plan was to glide path to handle SORR. Poor strategy, considering we were still partially working and had income to cover budget. Now, if the market tanked last year, I would have looked like a genius, but it still would have been luck. My take away is if you're still generating income, especially enough to cover costs, stay invested. I'm targeting 3 years of cash (majority I Bonds) to weather any stock market storm.
We also spent a TON more money than we thought on 2 major categories. We traveled a bunch (I know, weird in COVID, right?) and house remodel; $40k we didn't need to do. Got a second bathroom, so no real regrets there. A few things we didn't account for were small things like presents for kids/family, and activities for our 10 year old. That in itself ran us another $3600. Now, here's where everyone will jump in and say 'you spent how much on what'? We didn't HAVE to, but we could. Maybe it's not as Mustachian as others. But I learned another valuable lesson.
I dabbled in rental real estate, stock picking, having lots of cash, etc.. For the OP, here is what I think is 90% of the battle:
1. The only real controllable is your spending. Spending will dictate both the amount you can save while working and how long your capital will last once you stop working. I feel a little stubble growing on my upper lip...
2. Have a crazy safe withdrawal rate. My goal is to hover between 2-3% once we completely quit working PT. When working PT, goal is 0%. I'm counting on Social Security at 75%. I may have to withdraw a little more than 3% for a few years before I start collecting (I'm 48 now, like OP), but then once start collecting, I think I can reduce that withdrawal rate to like 1.5%.
That should get me 90%+ there, with things that I can't screw up and are controllable (how much I work, how much I spend, how much is left to invest). What I invest in exactly as long as it's diversified low cost mutual funds or ETFs, with 15-20% in cash/I-bonds, should do the trick. IF I could find a method to allow me to withdraw another 1-2% from my portfolio per year (currently at $1.7MM), that would be awesome. HOWEVER, it's that marginal return on time to try to figure that out AND a good chance I would DO NO BETTER OR WORSE than if I just kept it simple.
So I feel pretty bullet proof, even though I've made a ton of mistakes and continue to. I'm not completely FIRE, but I feel I could stop working any time if I got fed up with the couple hours a day of work. Now, if the economy tanks in a zombie apocalypse, then it really doesn't matter, so I don't try to plan for that.
Find a cash-stache that you think will get you through a major market poop. Is that 2 years, 3 years, 5 years? I picked 3 years. I have resources to do things like take out a mortgage, use credit cards, etc., to float another 1-2 years easily.
Bonds pretty much stink here. I-bonds seem much better, and I am working to park my cash there. I'll be 80-85% stocks. Probably put a few % of that into REITs. Real estate is great for some, but I've been there and not where I want to be. I'd rather work 2 hours per day PT from my home than deal with tenants. That's just me. I'm lucky I can do what I do and make decent money with such little effort, the result of building 25 years of a career in the same industry.
That's my own 2-cents, good luck OP! I've learned quite a bit from this thread and I hope you did/do too!