Welcome to the forum! You're in good company. I recently made the leap myself, though early 60's so not quite so early. Nonetheless, I completely sympathize with the fear factor and spending time here, getting opinions, reading success stories from experienced members, and commiserating with folks going thru the same kind of transitions got me over my OMY ("one more year") syndrome.
Like you, I've been steadily working since I was 13, worked thru college as well, including summers, never had any kind of real break until I quit my job. DW is quick to remind me that even vacations were usually disrupted by work. So, relaxing is just not in my nature. I'm one of those people who needs to be doing something in order to relax, lol. So, I have never really been keen on the idea of retirement, I never really wanted to early retire, and I figured I would keep working up to at least 65, if not 70. Partly, I actually enjoyed career quite a lot, and partly fear of not having enough saved (a notion this forum along with a dozen different retirement calculators have disabused me of). At any rate, I got the message that I was aging out and not moving up any further, that really pissed me off, I calc'd I have enough eff-all-a-yuz money, so I quit. And here I am.
Last pay check cleared a few days ago, so wondering if I'll go into some kinda of crazy panic attack. But, I don't think so. I could go back to work - just yesterday a former competitor called to feel me out for a potential role in their org. Tempting, but I will take at least a few months off to see how this FIRE thing is working before I consider something like that.
My advice to you is run a couple more of the other online calculators if you're feeling nervous, familiarize yourself with the various drawdown strategies, and read up on this forum the range of different approaches to FIRE - some folks able to do so on amazingly little budget, others with fat portfolios, but all able to make it work for them. One other piece of advice, and that is - don't be conservative with FIRECalc and other calc's just to be conservative - there's no reason to leave out SS. These calculators are already building in very conservative assumptions.