Good evening again Thephilistine, but however I'm not thinking that you're failing too much, especially in your lines of action and rhythm in your figures and poses, so other than that, I feel that you're on the rightest track indeed.
However, in order to make your gesture drawings the strongest in their looseness and liveliness. How would you like to time yourself with 90 more minutes of 30 second scribble figures, with a Timer app on your iPhone or whatever? The reason why is because if you do the timer app on your smartphone, then they can make you practices more than your addictive games, thus making your lines of action and rhythm the most totally and extremely liveliest and energetic.
Hope this suggestion had helped you too much for you. Good luck.