Why I draw upside down

I was making a new drawing and was using a lot of reference materials, pictures of landscapes, horses and a sky at sunset. I was working out the details of my sketch and my husband saw me drawing upside down. He asked me why I was drawing like that. Here is my answer.
Well, when I'm drawing every now and then I'll turn the sketch upside down. I do this because if I am struggling with something in the drawing that doesnt look right. I turn it upside down. Then I can usually see immediately the errors I made and can fix them accordingly. It gives you a different view point from the one you've been staring at for hours. I guess it's the same principal as holding your drawing up to a mirror.