The best advice I ever got about drawing from life* is: "Draw what you see, not what you know is there."
My mom told me this when I was twelve or so. I'd just finished drawing a portrait and couldn't figure out why the eyes looked all creepy and stare-y. Mom helped me to realize that it's because I'd made the whites of the eyes pure white - which is generally a weird look on a person. When I looked at my source material more carefully, I saw that the eyes were actually in shadow and nowhere near white - despite my brain insisting otherwise.
Later, in high school art class, I learned an exercise that helps us to "draw what we see": draw a picture from a photograph that's upside-down. That way, it's harder for your brain to make sense of what it sees and to impose your assumptions all over everything. Upside-down, most things are reduced to...shapes. And then you can draw what's really there.
*Or, as the case may be, drawing from a photo of a lady in a magazine...