When your body forces its own boundary


How your nervous system processes the cost of being 'on'

Hey Reader,

This week I was reminded of something I wish weren’t true, but always is: your body will set a boundary for you if you refuse to set it yourself.

As an introvert with an anxiety disorder for the past few weeks I've really pushed myself, first to ensure my first ever Introvert OS™ workshop delivered and also in preparing a talk for an HR conference.

Both were firsts and I really get into my head about firsts.

My talk was on The Strategic Power of Introversion. It landed well - both with introverts who told me they felt seen and validated and with extroverts, who told me I'd changed their thinking and inspired them to make changes.

For the rest of the day, I engaged with those who had come to speak to me and stayed at the drinks until quite late - because I knew this would lay the foundations of me potentially getting into organisations so I can help them make those systemic changes.

I did the whole being 'on' thing many of us can do for a short burst.

And then the floor dropped.

Not immediately. Not dramatically.

But quietly, a few hours later, like a system shutting itself down to protect the hardware.

I’d planned to catch up on work the next day. I’d planned to see my mum. I’d planned to write something polished and insightful for this edition.

Instead, my body forced a pause.
Hard.
No negotiation.

I succumbed to the virus I felt like I'd been fighting off since the start of November.

So here we are.

And if you’re anything like me, you know this pattern far too well.


Unbound Shift

Being 'on' costs introverts more.

Not because we’re fragile or socially anxious but because our nervous systems run hotter.

After sustained stimulation - visibility, conversation, holding the emotional load in a room - the body shifts into a mixed state that isn’t rest and isn’t action.

It’s something in-between. A depletion. A flatness. A kind of internal fog where even small tasks feel heavy.

A few things happen beneath the surface:

Your baseline cortical arousal stays elevated long after the event ends
Your brain doesn’t return to neutral quickly. It keeps processing.

Your prefrontal cortex burns through glucose when you’re in performance mode
Decision-making becomes harder. Emotional regulation dips.

Your immune system pulls back while adrenaline carries you
So the crash comes the moment the adrenaline fades.

Your body keeps replaying the stimulation long after you’re home
It’s why you can be exhausted yet wired, tired yet restless.

You don’t choose these responses.

They're hard-wired into your brain biology.

Once you understand that, the collapse makes sense. And you can stop treating it like a personal failure.


Unbound Step

Three things I’m reminding myself today:

1. Recovery is not optional

If I rest now, I shorten the dip.
If I push through, I create a long one.

Your system always collects the bill.

2. Visibility has an aftercare period

This is something we don’t talk about enough.

Introverts can enjoy being visible, but the nervous system needs structured recovery afterwards: warmth, quiet, pacing, nourishment, sleep.

Treat it like part of the event, not the aftermath.

3. Boundaries aren’t only interpersonal

They’re internal.

And the most powerful one is recognising your limit before your body screams it at you.


If you need a reminder of what boundaries look like in practice, the Boundary Setting Playbook is what you need. The link I shared last week didn’t work (thank you to those who flagged it).


So here’s a working link if you wanted it but couldn’t access it: grab your copy here.

In your corner always,
Sam 💛

Sam Sheppard

Introvert OS™

I share practical tools to help you design a life that actually fits.

P.S. When you're ready here are three ways I can help you:


1. GET THE EXACT WORDS:
Access the Boundary Setting Playbook for £17 - 20+ word-for-word scripts and a practical framework for saying no without guilt.

2. GET SUPPORT WITHOUT THE CALLS: Try Async Coaching - work with me for 14+ days through voice notes and/ or messaging. Get accountability, strategy and support that fits your introverted energy. Perfect for working through boundaries, overthinking - or any area where you're stuck.

3. GET INSPIRED: by reading my book, To Live, Not Exist - part solo travel memoir, part manual for living life on your own terms. Grab it here.

Let's connect! 👋🏻 You can find me on LinkedIn, Instagram, TikTok and Threads. Catch up with past editions on my website.

128 City Road, London, London EC1V 2NX
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