Nothing kills the mood more than a bad day, providing it with flavours such as bitterness and anger. Or is it perhaps the mood that is killing the day?
I personally believe that every day is neutral, and so-called bad days are just something we make them into.
When you feel that you are having a "bad day", you mind is going to look for more evidence to support what you are feeling, and it shall be found.
Good days are all the same. The day is no different, only the way you perceived it.