Hi Super,
Perseverance, that's all you need. You may want to try out a few different tools and paper, get your hands on the cheapest paper you can find, e.g. unused newsprint from your local newspaper. Every now and again, try to draw someone from memory, a gesture you've seen on the street or a school. Analyse your results. Are you missing knowledge in perspective, anatomy (needs time, don't study this too hard, unless that works for you)? Try to make each line count, or just play around, but consider that the audience will give each line a story, a meaning.
You may only need 30 minutes a day and in those 30 minutes, try to draw 30 or more figures. Draw the figures pretty small, but think big while doing so (consider the gesture, force, next action of the figure). Concentrate on your weeknesses, once you've identified them, but don't get too lost in them. Don't spend time patching up "failed" attempts. Put them behind you after analysing them for their failures. The analysing is just as important, you'll be surprised.
Stu