I found that practice on smaller pieces wasn't much help to me because real quilting includes the challenge of maneuvering the heavy quilt. I decided the only way to really improve was to quilt quilts. I practice the chosen design for a short time on a practice piece, and then take the plunge on the actual quilt. On one youtube video I watched, the teacher said you have to expect to make some ugly quilts. So start with the ones you're less emotionally attached to, and give yourself permission to 'ruin' some quilts. You'll find that after they're washed, they will look just fine.