As someone who gets in this state a lot due to stress and anxiety, I can recommend the following things:
1) As Callista said, keep yourself fed. What I often did was I would cook a large amount of a dish , keep it in the fridge and eat it gradually over several days. If you cant get out of your room, have some food in there. I always had a stash of granola bars and trail mix in case I had to hide in there for a few days.
2) Try to establish a routine sleeping pattern, and get up and go to bed at the same time each day. Set an alarm if you have to. I know this is easier said than done, but it's important for when you get back into the real world.
3) Be good to yourself, and try your absolute best not to see yourself as worthless or a failure. You just need a break. Put on a comedy or some cartoons, and laugh. Make a list of all the things you value about yourself and reflect upon them, and try some CBT exercises. Try your absolute best not to get caught of in the downward spiral of negative thought.
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Given a “tentative” diagnosis as a child as I needed services at school for what was later correctly discovered to be a major anxiety disorder.
This misdiagnosis caused me significant stress, which lessened upon finding out the truth about myself from my current and past long-term therapists - that I am an anxious and highly sensitive person but do not have an autism spectrum disorder.
My diagnoses - social anxiety disorder and obsessive-compulsive disorder.
I’m no longer involved with the ASD world.