The rule of thirds is something that aplises to a photo. You need to imagine your picture with vertical or horizontal thirds and the picture is not directly in the middle third. My picture is correct because the picture is in the first two boxes and the path is the last box. Your eye is drawn to the last third, where the path is going, it helps to make it more interesting to look at.
In this picture the tunnel is in the far third and the tree is in the secend third. Make sure there is some interesting in each third.