I think that you need to focus on understanding form and contour lines. the girl's body looks a little flat to me, and before adding the details in i would make sure that all my shapes and forms and anatomy is in the right place. the male's body is smaller than that of the reference, so you have to mind that too. and with regards to the gesture, yours looks a little bit stiff. try taking a break, then coming back to it after then hopefully you'll see where you got it wrong. :D

Humm... Maybe you could loosen up your lines and don't focus much about details? otherwise you can make the drawing look quite stiff. For gestural stuff it's better stay loose.