Drawing while only looking at your subject and not your paper can actually imprint that subject in your mind better than either just looking at it alone, or drawing while looking at your paper would. You will be tempted to look back at your drawing to see how it's coming along, but don't. Also don't be embarrassed if you're drawing comes out looking super ridiculous. The point is not to make a great drawing. If anything, just try to laugh at it.
You can see the process of doing a blind contour and hear more of my thoughts in the video below.
Painter of portraits and wildlife