I expect it’s more similar to the Buddhist idea that happiness is cultivated in your own mind. It’s driven internally rather than externally.

Specifically, meaning making. The same situation can be perceived as negative, neutral, or positive all depending on how the individual interprets it.

The classic example that's a bit wrong is a glass of water half empty or half full.

The true optimist doesn't see it as half full, he sees it as full. Half with water, half with air (being grateful for the air as well.)

The neutral person sees it as half full, and the depressive sees it as half empty.

That's near the opposite of what Aristotle intended. He wrote about happiness as virtuous action, living well. He wasn't so internally oriented.