Feed a cold starve a fever is remembered wrong the actual saying is feed a cold stave a fever. (meaning to hold off a fever) is actually not bad advice.
Have a bit of hair from the dog that bit you. How that became a hangover cure is beyond me started in something like 16 century England and if you were bit by a dog you were suppose to pluck some hair from the dog that bit you and hold it to to would to recover faster. It dosen't work for either problem.
If you are unable to sleep its because you are awake in someone else's dream
If you bite your tongue someone is talking about you