Three that come to mind:
1) Geometry challenged - but that is one of the reasons I chose quilting. I figured it would force my brain to work overtime during my retirement. It does force my brain to think, and I have noticed improvements in geometric perception. However, true dilemma is making my eyes and hands do what my brain understand. Something gets lost on the way from the brain to the eyes and hands. And that is why we have seam rippers.
2) color blind - didn't know it until I was in my 20's. I see the basic 8, but shades often baffle me. You have no idea how many quilts in magazines I think are ugly and wonder why anyone would make such an ugly quilt. When I read the directions, I find that one or more of the fabrics used are color invisible to me. I know there is something in the blocks, but the the color and/or pattern of the fabric look so washed out that they don't add to the quilt. Pastels do very little for me. Most of my quilts are made with 2 to 4 fabrics, high contrast, one focus fabric. I call them 'dramatic". I also make good use of my quilting buddies as color consultants.
3) Operator error. See 1 and 2, but impatience causes just as many problems as 1 and 2. And my best sewing is always done when the bobbin is empty - but at least I don't have to rip out stitches to fix that.