hey there, sorry to hear you are not feeling all right. I know the feeling.
If you got to a point where it's "that bad", then the first thing I would do is lower that level of emotional and physical stress as much as possible. Since this is being caused by thinking, you can't solve it by thinking. You must realize this to get out of there. You can't get out of your situation by thinking.
Step 1: Relax and rest your mind in nature.
I would take a 3-5 days trip ( 7 ideal ) camping/hiking trip *alone*, don't take your phone or laptop. Pick a trail that you can follow on a map, or just go camping. Keep it within your means. Don't prove yourself, and don't pick a challenge. Keep it simple, easy, and attainable. You should leave in the next week. Don't delay this.
Focus your mind on the problem at hand, and notice when irrational worries come in while planning your trip. Don't argue with them, just focus on finding the practical solution to it.
This is medicine for your brain. This will help you in several ways. First, it will help you focus on a task, it will show you the negative patterns in your mind and teach you how to overcome them with things within your reach right now. It will show you, you can get things done and learn when not to listen to the narration of your mind.
Just being in nature there will help you relax and recharge your body keeping you focused on all the work that camping involves. But you can turbo-charge it, and it sounds like you need to.
While you are there, find places where you can sit alone and feel the forest, the moment. Not by thinking about it, not in the interface of the mind, on the narration of thought ( label, judging, etc ).
But by experiencing it directly. You'll know you go it when you start to feel the beauty, listen to the wind, and notice small insects and slow things. This is not a goal, not a step to reach. It's the other way around, focus on resting your mind and the feeling of peace and healing shows up. And when it does, stay still, stay the same, in equanimity.
Don't force it, don't over-concentrate, don't "heat-up" your brain as a car going at max revs. If you get frustrated, remember is not about not being frustrated, but about taking energy ( power, attention, battery life ) away from the thought process that is frustrated. Ignore it and focus on something outside, on the feeling in you hands, on sound, sight, smell. Get out of your head.
Lowering "your thinking revs" takes time, you can't accelerate that. It takes 2-3 days in nauture, so take it easy. Things might and will feel strange, bad. Lot's of thoughts to leave got back home, compulsion about using phone and laptop, lot's of what-if's. Lot's of ideas that will solve all your problems if you go back. STAY until you can sit down on the ground and watch the leaves fly of trees. Until you can listen to the wind, look at a fire burn - all without thinking, without trying not to think. Just be still, do nothing, eyes open. Be. This is the medicine.
We don't get burnout by working too much, lots of people work 2 and 3 shifts and they are all right. We get burnout by a condition we did not know we had that makes us think and worry too much. Compulsively, until our brains get really tired.
We must learn how to manage this condition and our brains ( minds ). But we can't do this while in "burnout", crisis and certainly not by thinking and worrying non stop about the future.
Step 2:
Be prepared before you live for when you get back home. You will be successful, and when you get back you'll feel better. Try to have things organized, to take advantage of this breakthrough and apply all you learned in this "retreat" in your daily life.
You must be really focused on healing and recovering. The thought process will come back, it's a habit and a pattern. You must be patient and persistent.
Find people like this around you, try meditation, yoga centers, and qi gong centers near you until you find one that clicks.
Doing this ( not thinking, not worrying, not creating this context, this reality you are in right now ) must be your priority in life.
If you focus on yourself now, you will be ok in the future. Promise.
Remember it's not about getting rid of the feelings. Discover that your emotions, thoughts, and even the burnout it's not happening to you, they are just signals being emitted very strongly. Like error logs overflowing the system, you can't get rid of them or continue ignoring them anymore. Debug, observe, line by line, and you'll get it.
Happy to help more if this resonates with you: roberto@paz.co.cr