PHB pg. 204:???
According to what?
Cube
You select the cube's point of origin, which lies anywhere on a face of the cube's effect. The cube's size is expressed as the length of each size. A cube's point of origin is not included in the cube's area of effect, unless you decide otherwise. (emphasis mine)
Since your space is the point of origin, it's not included. It's kinda backwards, since you're pointing it back on yourself, but technically correct.