I think I just had a breakthrough.
I wanted to draw a jellyfish, so I started feeling it out, sketching a general shape & modifying it, changing things, & trying again, & I got into a flow.
That's the breakthrough.
I am so afraid of making "the wrong" marks that sketching is really difficult for me. I usually feel like I should be ashamed for not "getting it right" on the first go. To be able to actually sketch without shame is huge for me.