I think it's easy to cuddle / hug a human when falling asleep,
but once one is really asleep, the one who has his/her arm under
the other one's head will squirm in discomfort because the arm will
feel numb and painful but maybe you daren't move cause you'll wake
the other person up. 
Worse, if one kung-fu kicks in his/her dreams, then the partner
will become a victim of physical abuse! Some people enter the Shaolin School of
Martial Arts when they are asleep!
