I will attempt to guide you through this topic.
Let me start by saying this. I think you're being too hard on yourself because the clichés of how people react in stories is something that we all have to learn anyway, diagnosis or not. We don't usually write as reality is, we write as other people have written. Reality is just the inspiration for it.
What is a cliché?
Things we write are clichés, and writing is all about crafting a long list of written clichés that when put together (people we care about agree) doesn't suck, and isn't just one big cliché as a whole. Figuring out which don't suck, and when and why they don't suck, is very hard for most people and takes years of practice to start figuring out.
The knife sat on the floor, its silver blade stained with blood. Sophia's jaw dropped.
People's jaws very rarely "drop" in real life, yet if it is written like above most understand what it means, and that's why we tend to gloss over it as we read. If, however, a jaw first drops, and then immediately after an eyebrow is raised, and then in the next paragraph a fist is clenched ... then indeed it will be formulaic like you say.
Start by asking yourself the following question.
What specifically in time and space am I trying to describe?
Every word counts in a story. The starting point is to get yourself a more nuanced understanding of different kinds of situations and what people are thinking and feeling, so that you can imagine your own. Now I understand this might be part of your personal blindspot, but that doesn't mean you can't study typical situations and find some rules of thumbs and principles to eventually build an understanding. Let's break it down.
In the example with the knife, let's say there's a woman who finds it. Let's say it's in her house, and she thought no one had been in there since she left two hours ago. Now, she's walking into her kitchen feeling pretty okay, probably. She might be feeling terrible, but at the very least she's not feeling shocked - yet!
We assume things about how she's feeling (and what she's thinking) as she walks in, because the entire concept of "walking into your kitchen" is itself a cliché, so we know what to expect from her to some degree. She's probably not thinking "oh, I can't wait to ride this horse!" - there's no reason to think there's a horse in there. Similarly, she's probably feeling okay, because she's in her home ... could be worse, right?
Now she sees the knife. It subverts her expectations, because it has blood on it. How she feels and thinks changes, because this is a different kind of cliché than that of "walking into your kitchen" - and it's one she didn't expect, and one that usually means something bad is going on around her.
How do we write better clichés?
Your job here is to make the reader forget that you're describing something to them, and instead focus on what's happening in the story. Compare this knife reaction with the first, simpler one:
The knife sat on the floor, its silver blade stained with blood.
Sophia stopped. Her hand covered her mouth, lingering. Then she jerked back a step, the edge of the table striking her waist, her knees buckling. She shot backward onto the floor, gasping.
This is, if I can say so myself - a much better way to describe her reaction - and significantly more "Show Don't Tell". Let's break down some of what's going on in it!
- The knife sat on the floor, its silver blade stained with blood.
By describing this knife, we're implying that she's seen it. She's seen the blood. This is the context for what comes next - so we know what she's reacting to.
- Sophia stopped.
The first step of her reaction is to simply stop. This conveys that she's noticing the knife and is now paying attention to it, which makes sense because she just came from what we're calling "the walking into your kitchen cliché". The stop prepares the reader for the fact that she's about to have a reaction, so if the readers weren't paying attention already, they should be now.
- Her hand covered her mouth, lingering.
"Covered her mouth" is another well-known cliché, but we're not using it to stand in as her whole reaction, we're using it to describe a part of what's happening in the scene. The gist of Show Don't Tell is exactly this, you describe what's uniquely happening instead of the generic situation. After all, what's a reaction? It's a re-action - an action that follows another. And "lingering" at the end there is a way to signal that she's still processing the scene, because she's pausing in the middle of her reaction.
- Then she jerked back a step, the edge of the table striking her waist, her knees buckling.
Sophia understands that there might be immediate danger in her home, and the place she assumed was safe isn't. She's panics, and we know this because she's jerking backward. No one jerks backward randomly after seeing a knife, it must have triggered some kind of negatively motivating feeling, right?
We further realize this by how she bumps into the table. She's not paying attention to what's behind her, because all of her attention is on the threatening situation. That's another way we know how overwhelming it is. It even causes her knees to buckle, connected to another cliché of "legs weak by fear". Finally she falls, and when she falls it's backward because she's instinctively moving away from the knife.
- She shot backward onto the floor, gasping.
Is she gasping because of the knife, or because the table startled her while she was sensitive to threats, or because of falling? Narratively speaking, probably a bit of all three, as it all adds up to her shocking experience. The reader doesn't always know the exact details of what causes what in a scene, and sometimes not even the writer knows. But it's telling us a story that distracts us from the clichés we're using, and that's what we are trying to do here.
All of this shows us what her reaction is, by having us read about it as it's happening - without having to be told like this:
Sophia stopped. Her legs were weak with fear, and she fell back as she tried to move away from the knife.
The point of Show Don't Tell is to know what's really going on in your scene, and then describe what we would experience if we were there (the exact boundaries being determined by Point of View). You don't have to tell the reader something if they can make the connection themselves.