hello! mind the typos, etc, i'm writing this in a rush since i have to go in like, 30 mins
i still struggle with this problem a lot myself, but i think one thing that has helped is studying less classically. that is, studying not from photographs for peak accuracy, but studying from illustrative masters and in particular, animation. the key for me was studying from 3d movies-- i did a lot of studies from rise of the guardians (2012), how to train your dragon (2010) the thing about poses in animation is that they're boiled down and exaggerated to communicate exactly what needs to be communicated.
if you're looking for something less cartoony to study from, i might suggest browsing through NMAI's collection -- https://americanillustration.org/collection/ and wiki-arting whoever catches your eye. a favorite of mine (he's cliche, you might know him) is JC leyendecker. his work is very commercial, but he exaggerates just enough in the right places that his illustrations are extremely eye catching.
obviously, you already have a lot of the classical concepts down, and have a very specific amount that you're progressing day by day. i think the key now if for you to start exaggerating where you feel comfortable-- for instance, with some of your studies. what if the figure's arm reached out a bit further to really jab the knife in? if what you're feeling in your art when you're finished is that it's stiff, uncomfortable, or uninteresting in some way, i think you need to consider what narrative you're attempting to carry through in the interactions you're portraying and exaggerate bodies to express that.
as a frame of reference, when i studied animation, our 2.5 hour classes were structured like this:
- 5 minutes of 15 second poses
- 5 minutes of 1 minute poses
- 15 minutes of 5 minute poses
- 40 minutes of 20 minute poses
- (break)
- 1 hour pose