KIRK: Spock says this could be an historic occasion and I'd like to believe him. But how on earth can history get past people like me?
This is the question that consumes Kirk throughout The Undiscovered Country. How are people like him supposed to adapt to a new world in which everything they take for granted isn't true anymore? That'll really throw your head for a loop…
SPOCK: This will be my final voyage on board this vessel as a member of her crew. Nature abhors a vacuum. I intend you to replace me.
Spock is going through his own personal crisis, though in his case it revolves around the future of Enterprise. Like the rest of the crew, Spock will be saying goodbye to the ship he's long called home, and he's concerned about who will replace him. But who can replace Spock? That's impossible.
GORKON: You don't trust me, do you? I don't blame you. If there is to be a brave new world, our generation is going to have the hardest time living in it.
Gorkon knows exactly what's going through Kirk's head. Both men are relics of an era that's about to go kaput. The only difference is that Gorkon is working to build a better future, while Kirk is content sitting on his butt. Regardless, they can both be described as "grumpy old men," if that's what you're wondering.
McCOY: Three months before retirement. What a way to finish.
KIRK: We're not finished.
McCOY: Speak for yourself. One day, one night—Kobayashi Maru.
The "Kobayashi Maru" scenario is an infamous test in Starfleet Academy that is literally unwinnable. As legend goes, Kirk beat it by hacking the program. That's top-tier trolling, if you ask us. Context aside, McCoy is grousing about how ironic it is that their future was torn away from them just as it was within their grasp.
KIRK: I was used to hating Klingons. It never even occurred to me to take Gorkon at his word. Spock was right.
Finally, Kirk understands what Gorkon was trying to say all along. Their generation is marred by prejudice and distrust, but future generations don't have to travel down the same path. (Sound a bit like the Cold War generation to you?)
SPOCK: Is it possible that we two, you and I, have grown so old and so inflexible that we have outlived our usefulness? Would that constitute a joke?
His humor might be ehhhh, but his analysis of the situation is spot-on. Spock and Kirk have a great deal of wisdom and experience worth treasuring, but these same qualities also sometimes limit them from appreciating alternate points of view. This is a natural consequence of aging, to some extent.
UHURA: We're to put her back into space dock immediately to be decommissioned.
SPOCK: If I were human, I believe my response would be, "go to hell." If I were human.
Most Star Trek movies include a moment in which Spock uncharacteristically utters a cuss word, and The Undiscovered Country is no exception. In this case, it's used to illustrate the crew's camaraderie on the eve of their obsolescence.
CHEKOV: Course heading, Captain?
KIRK: Second star to the right and straight on 'til morning.
This is a small moment, but it shows that Kirk has not given up his adventurous streak just yet. He might be older, but he's still the same rogue he always was.
KIRK: This is the final cruise of the Starship Enterprise under my command. This ship and her history will shortly become the care of another crew.
For Trekkies like us, Kirk's final audio log is quite moving. Through the log, he finally makes peace with the fact that the world—and his place in it—is going to be very different in the near future. But that's okay. The important part is trusting the people who pick up the reins.
KIRK: They will continue the voyages we have begun and journey to all the undiscovered countries, boldly going where no man, where no one, has gone before.
Here, Kirk echoes Gorkon's thoughts on the "undiscovered country" of the future. This is a great way of emphasizing the respect he's developed for his former foe. It also cleverly references Star Trek's opening monologue to remind us that this is not actually an ending, but a new beginning. Maybe even...a next generation. Nailed it.