I didn't even try to miter my first 2 quilts. The 3rd one I just finished I tried it. It wasn't perfect and I started to really get frustrated, but decided that I have read so much on this board about how there aren't really any 'quilt police' and that it didn't look horrible even though not perfect. After reading these guidelines I know more of what I did wrong....which is stopping exactly with the same seam allowance you are using. I used a 1/2 inch and stopped a 1/4 inch. Not too old to keep learning something new. Never learn unless you try! The next one will be better for you.