Regarding the effects of a mirror reflecting your image while you're sleeping.
From the 1st level workbook:

Quote:

It'll tend to scatter thoughts and create negative dreams. It can also double your health issues, create loneliness, or complicate a marriage through a third person.




And the solution:

Quote:

Move all mirrors and reflective surfaces such as television screens so you cannot see your image in bed or cover them before going to bed.




From what I understand, if while on the bed, you can't see your image on the mirror, there shouldn't be any problems. Then again, maybe there're more little distinctions which I'm not aware of yet.