Do not let people see your work before you've finished the first draft.
Or, as Stephen King says in his book On Writing, write the first draft with the door closed and the second draft with the door open.
I know this, KNOW it, and yet still I succumb to show-it-to-someone-itis. It's like my inner four year old has just drawn a picture with a brand new box of crayons and can't wait to show it to someone. More often than not, if incorporate their feedback, I end up taking it out because they haven't read the entire thing so don't know how it all ultimately fits together.
Not to mention it can wildly sidetrack one's creative vision. For example, I've lost a year with this mss because I let myself get tangled up in too early feedback.
Some day, I will learn. Or more importantly, remember. But I share this with you, grasshopper, to spare you similar headaches.