I am an optimistic pessimist. I usually find the positive although I realize there is a possibility of negative.
Personally it depends what is in my glass. If it is guinness that sucker's gonna be empty real quick! But just as fast it is gonna be filled right back up.
It isn't the glass you should focus on though it is yourself.
An optimist will find ways to keep their own glass full.
A pessimist will fail to fill their glass and blame it's emptiness on anything but themself.