I think happiness is an inevitable byproduct of honestly following your innate sense of self. Intelligent people can be dishonest with themselves, not know themselves and be (more) capable of lying to themselves and coming up with justifications to do what they mentally want (rather than following their innate sense), thereby trapping themselves in endless dishonest but justified loops.
This tracks with what I've seen. Greater "capability" can imbue a greater ability to lie, cheat, deceive oneself, or others, and generally create all sorts of complicated problems, be them internal or external
