One of the reasons I roleplay is to practice the description of motion and body language. To convey emotion through showing, rather than telling. To display an emotion through gesture and form rather than outright handing it to the reader.
I've had some success with this. I've had people pick up on things through a character's body language (as written) without having to outright state what is being evoked. I always check in, 'Hey, she's sitting like that because...' 'He did that gesture as a...' since I figure hey, their character would know this, even if they didn't pick up on it. And often? People say they got it.
Even better is when I've been threading something subtle through a scene and someone later goes, 'Oh shit! I just realized...'
To me that's success. For as much love as I have for snarky asides and meta-jokes at my character's expensive, I love even more when my writing is immersive enough to draw the other player(s) in.
All this to lead to this video: https://www.youtube.com/watch?v=GfqD5WqChUY.
It's about camera direction and acting in regards to immersion (David Fincer, verily, is a god unto men), but it showcases, to me, just how vital that display of body language is. It's not enough to just show it in Fincher's world, but he wants to pull you in and sweep you up in the moment through the camera.
I strive to do the same through words.