Satisfaction is reality minus expectations.

"Smart" tends to be used in a way that includes intelligence (rate of learning) and knowledge (how much is known).

Satisfaction comes from accepting what is outside our control (accurate expectations), and making continuous progress/improvement on the parts of our reality that are within our control (our own perceptions and actions).

Intelligence and knowledge maybe don't correlate as much with wisdom as one would expect. I have met people who learn slow and don't know much but are very wise, and satisfied.

Lastly, happiness is always fleeting. Happiness can't be enduring, but it can be blocked by ego and high expectations. Satisfaction can be enduring, but correlates with virtuous actions, not intelligence.