set your machine speed to what sounds like a comfortable speed. That is rev it up. However, don't try to go fast but rather a medium speed. Then practice moving your hands in sync or balance to the speed of the machine.
Just doodle until you feel comfortable. Keep doodling until it feels right. Now, don't ever let both hand leave the quilt at the same time. If you do you loose control.
If you feel you need to move a hand for better control then STOP the machine with needle down while still holding the fabric and repositiokn hands. Start the machine and let it stitch in place until you have control. Don't get in the habit of moving your hands when the machine starts, the first stitches will be reallllllllly big. I don't agree that faster is better. Go the speed that gives you the quality of the stitch you want.