The larger seam allowances for clothing ( 5/8" ) were to help with the fabric pulling loose at the seam when under stress. For quilts, the 1/4" seam allowance is plenty for one main reason - since the three layers are all quilted together all over the quilt, the individual pieces or layers are not under any stress from pulling. When you pull on the edge of a quilt, you pull all three layers at the same time. I've been sewing clothes since I was 9 years old (learned for 4-H) and I know how hard it is to get the 1/4" seam burned into your brain. Practice is your best friend when making quilts - use scraps and make lots of little things like potholders, dog beds, and such. Your 1/4" seams will get much better, as will your piecing and quilting. Then when you make something to show off, you can be assured that you did it right!