Easy and difficult points

Alright so, here goes again. I am too forgetful. This should be done on Thursdays, but I keep forgetting it.
So, without further ado, Easy and difficult points during the last lesson:

Easy: I think that making the shadows, once I knew where to put them, was easy. I chose some pencils in varying softness, and drew some lines, which I later rubbed out to create fairly successful shading.

Difficult: I think it was difficult to draw the actual features of the face, because I saw it as a face even when the picture was upside-down. I did get a relatively good result in the end, but I think I could improve it.