Well, I have the same learning curve problem - it can be frustrating to try and do the fancy stuff only to have it look horrible when you are finished. One way I practice is two pieces of muslin with some scrap batting and I just go to town on that piece just for practice.
When I first got my longarm - I actually ripped out all the stitches on one of my quilts because I just didn't like it. I still cannot do the fancy stuff but I am trying. Hopefully it will get easier with practice. Just know that you are not alone....