Things you need to try and focus on while quilting:
- Keep your shoulders down, it's very common for quilters to draw their shoulders up to their ears. This will result on back and neck strain - you don't want that, or you'll need recovery time before you can quilt again!
- Your needle speed versus your speed moving the quilt around. You need to find a happy balance of how fast your machine is going, versus how fast you are. If your stitches are very long, you are moving too fast or your machine is not stitching fast enough. If you're stitches are tiny and close together, nearly perforating your fabric, it's likely that you are sewing faster than you are moving your quilt around under the needle. Of course you may see a combination of both issues, some long, some short - it's really a matter of slowing yourself down and practicing the feeling of moving the quilt around.
And here is a picture: