Your machine definitely needs to go faster than your hands. If you have a speed control for your motor, you might set it at what seems appropriate and that would be one less thing you have to worry about.
Also, curves and circles are some of the hardest things you can do. When you go around the curves, you have to slow down just a big, otherwise you get those stitches that are quite a bit bigger than you really want.
And just do what everybody else is saying...Practice! Practice! Practice!