What word describes someone who isn't exactly optimistic, but has a positive outlook?

I need a word to describe someone who knows better than to expect the best, but can be happy in unfortunate circumstances.

I know phrases like "positive outlook" and "good disposition" could describe such a person, but I don't know any single words that would.

To differentiate between an optimist and the person I'm trying to describe:

When asking for a promotion, an optimist will expect to receive the promotion. The other person will hope for a promotion, but won't be disappointed without it.

A person with a “positive outlook” could be described as a positive person. You could say he has a positive personality.

A positive person will hope to receive the promotion, but if he doesn’t he won’t be disappointed.

From dictionary.com:

positive
9. emphasizing what is laudable, hopeful, or to the good; constructive: a positive attitude toward the future; positive things to say about a painting.
10. not speculative or theoretical; practical: a positive approach to the problem.

You could describe a person who "can be happy in unfortunate circumstances" as sunny -- cheerful.

Your example describes a person with a glass-half-full attitude. In the link to Wiktionary, the definition is given as "optimistic," but to me it is slightly less in that direction, and more someone who would make the best of whatever life sent their way. If you really want a single word, however, go with sunny.

Will a realist do? A fatalist will succumb to faith, a pessimist will accept the worst, an optimist will always be disappointed, but a realist sounds just right. Doesn't he?