I would say optimism brings joy. The type of optimism though can determine how real the joy is and how long it is sustainable for.

I recently encountered the idea that there are three types of optimism;
Dispositional Optimism: “Dispositional optimism is a generalized expectation about your future”
Explanatory Optimism; Like the name suggests, this type of optimism has to do with how you explain why certain things happen to you.
Unrealistic Optimism; At times, feeling hopeful about the future is part of a thought pattern that isn’t entirely logical — this is known as unrealistic optimism.

Read more about this here.

The first two are susceptible to influence since the first seems to be based on nothing except chance (or genetics) and the second on ones intellect and narrative. The third is not logical so it may stay stable.

There are two types of "isn't entirely logical" optimism. One is illogical because it is below logic, less than logic. The other is above logic, beyond logic. What is beyond logic? Faith.

When faith drives our optimism it brings a sense of joy; a sense of joy that comes from surrender to that which is beyond our comprehension.

The walls of G-d's home, the Mishkan, that we learn about in this week's Torah portion were made of wood either acacia or cedar. In Hebrew it is called Shitim. Our Rabbis understand this word to mean folly, not logical.

There are negative behaviors that we can attribute to the illogical. Not acting in concert with the world's standards. Falling into line with what society tells us is normal. Pandering to the judgement of the world.

Then there are the positive behaviors which we attribute to that which is above logic. Doing what we know is right, even if the world or our society tells us that we are crazy.

The former, doesn't breed joy, it breeds insanity and madness. We feel controlled and resentful that we are accommodating society. Many young people rebel against this notion.

The latter, moves us to a place of surrender to something bigger than is. It breeds joy, confidence, a real inner confidence that pushes us through the hardest, darkest and most challenging of times and raises us above all of the world's craziness.

These days as a Jew it can feel like we are being asked daily to choose the illogical. The Parsha tells us that to build a Home for G-d we need to go beyond logic.

Stand strong! Identify what exactly the world is telling us to do or not to do and it's probably a sign that we need to do the opposite. Together we'll build a joyous home for Hashem!

Am Yisrael Chai
Good Shabbos!