/ic/ - Artwork/Critique

I want to get really good at drawing from life. Around 8 years ago I was into drawing, attended life drawing classes, did maybe 1/2 of some /beg/ book (keys to drawing maybe), but then I kinda fell off.

I drew this girl who was sleeping in the same room as me this week. I think I more or less captured the pose but I didn't go into much details. Maybe it's not a very "serious drawing", because I just whipped it up in like 10 minutes, but I figured I would include it to help my post have some more visibility.

Should I just draw everything I want and grind like that or is there some theory or book I should take a look at concurrently? I remember stuff like measuring with the pencil, drawing imaginary lines to check proportions, drawing negative space, but I never learned much about construction for example and simplifying into elemental shapes.