Don't be discouraged, I am still learning after years of trying to make blocks that come out the size the pattern says they should. My plan for the summer to try and work on perfecting my piecing is to do some of the exercises in Harriet Hargrave's Quilter's Academy book. There are some nice projects that focus on getting that 1/4" seam using rail fence and 9 patches. Also includes lots of expanations on preparing fabric, cutting techniques and setting up your sewing area. Then next year I am going to work on the projects in the next book in the series.
Here it is at Amazon -
http://www.amazon.com/Quilters-Acade...7802466&sr=8-3