The kind of thread you're using could make a difference, too. My preference is King Tut by Superior. Make sure you're using a new Top Stitch 90-14 needle. (I change my needle after every quilt project.) You might want to consider taking a class (in person) with hands-on help. There are a lot of very helpful books out there, too. I agree, the secret is practice! Make several practice sandwiches ~12 x 12" or even a little bigger. Use the Machingers quilting gloves. Drop the feed dogs.

BOOKS: Free-Motion Quilting Made Easy, by Eva A. Larkin, Guide to Machine Quilting, by Diane Gaudynski, & Free-Motion Quilting, by Angela Walters were the most helpful books for me. They'll be cheaper from Amazon than your LQS. The Leah Day tutorials on YouTube also are very helpful. Keep trying. Good luck! JCY