TOS #24: This Side of Paradise

This episode is about the Garden of Eden. In it, all these very healthy-looking guys live blissfully in this Smurf-like one-woman colony. This woman actually loved Spock 6 years ago, and uses these weird bliss-making spores to make him decide to stay in Eden.

Eventually, the whole crew submits to the spores, falling into soma-like trances, until the Captain figures out that strong emotion breaks their hold on the mind. He pisses Spock off enough that Spock can overcome the Spores, and then they all agree not to court-martial each other.

Spock is acutely aware that he gives up his only chance of happiness, but that's OK, because being blissful yet having nothing to live for is no good, says Captain Kirk.