Theresa, I think as you get more experienced, you'll be able to look at a lot of blocks and figure out what you need to cut to make them. I almost never follow the cutting instructions on quilterscache blocks. In looking at the block you made, which is a beautiful block by the way, you know you need to make 12 3-1/2" half square triangles. Make them whatever way is easiest for you. I would make them by cutting each of the two fabrics into an 8 x 12 rectangle and marking it into 4" squares, then drawing diagonal lines on the back of the light fabric, stitch 1/4" on each side of the diagonal lines, cut them apart on the drawn lines and square them up. I find that a lot easier than cutting a strip, cutting the strip into squares and then sewing each one. Everyone has their own favorite way of doing things.
You're doing a great job, so don't let a little mishap get your down.