Every. Single. Day.
I doubt you’re alone in feeling this way.
If you can, save save save as much as you can so that you have a nice comfortable safety blanket to be able to keep yourself afloat if things go cold.
Saving is something i need to do more of for sure. Transferring money to my savings account lifts a little of the anxious weight every time. And when I have it transfer some of it back to pay for direct debits etc .... ohh the ache ! And the worry ! Ugh! Not worth it.
Work all you can while you can, within mental and physical allowance.
Save save save whilst also allowing yourself plenty of treats to keep moral up!
Make some goals, literally write them down and tick them off, I do this and it helps me keep my head level, keeps me actually going to work, I know when and how much I need to have earned and saved away. It’s when I don’t meet my own expectations that I worry most.
But keeping literally lists means I know where I stand from week to week.

I constantly worry about when my last booking will be. Will it all stop dead in the new year?? Will I only last til my late 20s and then nobody will want me ?? Will review sites become so disgusting with their lies that I pick up a horrid reputation?! Ugh !

Having a nice comfy savings account keeps the nightmares at bay, mostly.

Remember that savings can be taken off you if you end up in a home.

I agree with what Eve said but also invest and invest more, fill your ISA every year and if under 40 you can open a LISA where state  give you free money and you will be just fine.

I just went through this in several weeks off with a bad chronic pain flare up. I realised that I was winding myself up & I just had to triple check my accounts & get things in better perspective with my health.

Anxiety/fear is often caused by unprocessed emotions. So in this case, grief, with the previous situation you mentioned. When you are having times when you say

"I became defensive and rude when dealing with various attacks. Due to the level of work I find myself tired at times as well and it sometimes causes my performance to worsen - this has been picked upon and discussed"

This is all normal. It's important to take time out or reduce your work load when you feel frazzled. That's when all these anxieties & defenses become amplified, isn't it. There's always going to be naysayers, their opinions are just that, their opinions. They don't know the full picture & wont care to. Sod 'em. They are people who you never have to see again & probably wont ever want to, right.

I have sleepless nights wondering what we would all do if Adultwork went down. It’s making me think should I be getting a mortgage because how could I pay it if we didn’t have the sight. I never had anxiety before doing this job 4 years in riddled with it.

Well this proves why advertising in only one place is a crap idea, surely?

The punters don't all disappear just because one site goes down, they just go to a different one. The more ads you have up the more likely they'll find you and you'll have a huge advantage over all the people who didn't bother

Yes, ugh. I've left this industry three times and always come back. Like every job (self employed or not) there is no guarantee of continuity or income but there are things you maybe can do:
Save save save!
Spread your advertising across a few different sites.
Do not depend on one white whale customer or client.
Use your time not working wisely; a course or uni, or night school, or part time job or volunteering.

Regarding punter forums, just don't. They're not representative of your client base and form only a small percentage of men who will pay for sex.