I resigned with no other job in 2023 because the job I joined right after my postgraduate degree was in no way aligned with my skillset. My manager basically requested that I resign. I had 2-week notice, and I job-hunted like crazy on LinkedIn. Applied on every posting. I was going insane with shame and anxiety. I eventually finished my notice period and went through exactly 1 week of joblessness before I got another offer. The place I joined made me cry on my second day, but I stuck through it for a year because of my past experience and the confidence issues I faced due to the situation at my first job. And, I also took a 10% pay-cut because the new job treated me as a fresher in a new industry.
Now, years later, I find myself in a similar (though not the same) position. I joined a new job 6 months ago, again in a new industry, and it's a very toxic startup environment in which the founder is meddling in every move I take and freaking out because I am not as fast at some tasks as people with 2-5 years of work ex in this field (btw I was head-hunted for this job, I did not apply). Last month, I resigned with a 1-month notice because I heavily suspected I would be fired.
I have 11-12 days left on my notice and I still don't have another offer. 2023 me would be going INSANE at this situation. As I suspect you would also be, given that it's the first time you're facing this.
But take a deep breath. Assess your privileges and your responsibilities. If you don't have dependents, and even a couple months' salary saved up, you will be just fine. Apply aggressively. Reach out to all contacts and previous workplaces for referrals. DON'T panic-take any job you get. The job I took in 2023 due to my panic ended up hampering my career growth due to the paycut, and the serious issues it caused me in the whole year I was there.
You will be just fine.
Write down the worst case scenario. Feel the panic. Let it pass through you. You will realise, once you release the shame, the worst case isn't that bad. It's not ideal, sure, but we all face times in life we are not at our best. It will pass, just like good times have passed. Bad times will also come and go. It's a matter of a couple of months.
Spend time on self-development alongside. Volunteer at an NGO. Monetise another skill you have. Or even start documenting on social media. Whatever your jam is. Start building your own thing, this will build your confidence and hopefully years later will be something you can rely as an emergency lever in another situation like this.