Check out your shadow. Unless the light source is very close, very bright, or both, most shadows fade the further away they get from you, or if there are other lights from other directions weakening the shadow. Making your shadow fade, however, is easy. To do so:
Click on the shadow layer. In the layer's palette, click "Create Vector Mask." It should be right next to the Fx from earlier, and is a square with a circle in the middle. Click on the white square that appears in the layer's palette. Select the gradient tool (press G), and use a normal linear gradient. Create a gradient across the face of your image. To lessen the effect, lower the opacity in the top bar.