I prefer a glass half full, because then I can buy whatever fills the glass at a better price than the glass at the right size. If I have two glasses the right size, they would cost more than a double size glass unless the double size glass needs reinforcing in order to take the pressure of the bigger load. If I have to stop drinking while the bigger glass is being filled, then I would be better off with two right size glasses so that one can be filled while the other is being consumed. If I had a glass half empty, I would be a genius because there are laboratories all over the world trying to achieve a space with nothing in, which would not exist because it's nothing (I think). Therefore my glass is always full with varying amounts of liquid, powder, dust, and gas.