There are times when i get tired of working on 2-D works, paintings, drawings, etc...
So i work with 3-D projects.
And i've noticed that working this way helps me in the 2-D realm. The moment that you try to sculpt a 3-D form you begin to understand more of the shadows and curves that make up the shape.
To wrap your mind around a painted object, it seems like, you need to physically make it first.