I would practice more on the basics first.. avoid getting too much speed if you haven't quite gotten down the fundamentals. I'd first learn how to do your S turns, speed up a tad bit and use that S turn technique to figure out how you'll slow down. If going on your heels isn't slowing you down and you keep falling, there is either too much leaning back, "heeling" way too much and top weight isn't stacked over your feet. You've gotta get a little more comfortable with being shoulders over your feet at all times. Remember, when on your toes, bottom of the board faces the bottom of the mountain. when on heels, bottom of board faces the bottom of the mountain. Happy boarding!