Optimist in a sentence?

An optimist is someone who always has a positive view on life.

The optimist always lives longer than the pessimist.

I depends on what kind of sentence you're looking for, but one that I think is quite good is "A man who is inspired by the starry sky from inside prison bars is truly an optimist."

Always the optimist, she knew she'd go on with her life although she was out of a job.

In modern English I wish I were an optimist is correct. Remember that was is the past tense. That sentence is talking about something that the subject is not, so it means: "I am not an optimist, but...