If someone is having a shower in the other bathroom you should think twice and remember the time when all of the sudden the water temperature fluctuated and you got scalded because someone flushed the toilet. Almost everyone has had this experience and believe me it is not pleasant!
5. There is nothing to be afraid of
It is safe to say after so many researches that pee is actually cleaner than your saliva. You do no harm to anyone if you leave it there.