I think what hindered me the most in drawing expressions and trying out new poses when I started drawing, was that my faces were so constricted and I tried too hard to make everything look perfect - so they often ended up being anything but perfect.
I’ve learned through the years to really just let loose and have fun failing because it’s much more fun to play around while drawing than trapping yourself in a box of rules and being afraid of what people might say about your work. Of course it’s important to know the basics of anatomy, how the face works etc because it makes it easier to break the rules once you know them. But if you feel like you can’t relax and you’re constantly stressed out while drawing because you have all these “the face needs to be like this” and “the hand like this” running around in your head, then you’re doing it wrong. The most important thing in my opinion, is to really just have fun and not give a damn. I mean c’mon, half of my drawings are strange sketches with poses out of this world and 99 % of the time I don’t know how to draw feet but I still keep drawing Jack Frost because I like drawing him.
When it comes to expressions - actually that is my weak spot when drawing. I constantly draw a lot of the same expressions with a few changes here and there as I am still learning when it comes to that, and I think the reason why it looks so simple is because I don’t know how to add more lines without screwing it up HAHA but really, I don’t know how to explain myself with this in writing as I honestly do not have the faintest clue in how to explain it other than just; have fun.