You are being too hard on yourself. But yes it does take practice. I do a lot of pantographs and recently started using rulers. I try not to be so hard on myself because after the quilt is washed it makes a difference also once you stand back a look at it, it looks so much better. Your looking closer than what most people would. Just keep practicing and yes a grease board or sketch pad is a great way to practice. Just have them while your watching tv and you will be surprised at the progress you will make.