Optimist

optimism |ˈäptəˌmizəm|
noun
"1 hopefulness and confidence about the future or the successful outcome of something : the talks had been amicable, and there were grounds for optimism.
2 Philosophy the doctrine, esp. as set forth by Leibniz, that this world is the best of all possible worlds."
• the belief that good must ultimately prevail over evil in the universe.

oxforddictionaries.com/us/definition/american_english/optimism