Being optimistic, which in my opinion is trying to look at the bright side of things and expecting things to go right is not a good way to live. On the flip side, neither is being pessimistic and thinking things are always gonna go wrong and just being a general downer who no one (friends, girls, family) wants to be around.
The best way to live is just take what life gives you and focus on improving yourself. I'm with whoever says when you expect things to go one way, they go the other way 90% of the time. It's just the odd way the world works and thinking about things like that leads me to feel like there is some higher purpose or afterlife, some forces controlling our lives, but anyways back to the topic. If you try to be happy all the time and try to expect the best all the time you'll never actually achieve satisfaction or happiness, you'll always be dissapointed with the outcome of situations, and you'll come across as fake and smug. Likewise if you're sad and always expect things to go wrong, your life will just be shit, and you're the most likely type of person to either kill someone else or yourself(no offense to our pessimists, it's just reality). Like most things in life it's best to take the middle ground, expect nothing but be ready for anything, and you'll be happy with what good does come, and you won't take as harshly the bad that does come.
I actually think about stuff like this all the time so I'm glad someone brought this shit up