I just took a look at this in this small image format and noticed how monotone the painting is. Its a problem I always have when I paint outdoors. Its pretty much all midtones. When you are working under a strong light source (i.e. the Texas sun) you have to really push those values! I converted the image to grayscale in Photoshop to see how well and truly in the middle I was.
I also wanted to mention that the strokes noted on the side note each one I painted in order.