Optimism is a positive feeling about a situation or condition. The optimist is a person who 'always sees the bright side' or has expectations of good results. The optimist is also often derided as the person who sees the bright side with or without a reason. In common usage the term is normally qualified to describe its context, but to call someone an optimist implies that they're hoping for too much.

Voltaire's Candide: A satire on the optimistic belief that this is the best of all possible worlds.

I'm a natural optimist.

That's just the problem, you're a natural optimist.