> 2. "Happiness depends upon ourselves."
he's quiet possibly referring to happiness as a relationship (with family, friends, colleagues, citizens etc) rather than just by oneself / isolation / individual. he famously said "man by nature is a political animal" (or social if you prefer)
Social and political are very different, unless you are overly concerned with accumulating power within your social relationships.
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.