Darth Vader was not a sentimental man, unlike his previous incarnation as Anakin Skywalker. He did not fear pain or death, and had no reason to appreciate the small things that in his life. Where Anakin might have desperately wished to bring his mother back, to save his beloved wife, Vader did not. It was ironic that he, the Jedi-slayer, felt closest to their teachings now that they were extinct and he was one of the last Force-users left...he recited their ancient mantra in his mind again:
There is no emotion. There is peace.
There is no ignorance. There is knowledge.
There is no passion. There is serenity.
There is no chaos. There is harmony.
There is no death. There is the Force.
Yes, it was ironic indeed. He had been raised as a slave-child, then as a Jedi, and was now a Sith Lord. He had made his childish promise to go back to Tatooine and free all the slaves, but never fulfilled it. Why should he? That world held too much pain, too much suffering. It was steeped in the Dark Side of the Force, just like he was, and couldn't possibly be worth the trouble it would take to save it.
A Jedi must have no attachments.
Again, the irony. As a Jedi he had broken all of their rules, foregoing the celibate life and giving in to his emotions. He had flown into a blind rage with the death of his mother. He had eventually caused the death of his wife, whose relationship with him had been illicit from the beginning. Now, as a Sith, he held no pity or compassion, no hatred or anger, no joy or fear.
He was at peace with himself and his circumstances, though his visions of death and destruction had grown so frequent as to prevent him from sleeping. While he could never guard himself in his dreams, which never ceased to plague him with their uncountable "what if" circumstances, his powerful mental defenses rose as soon as he would wake. He would breathe deeply in his meditation, breaking his attachments for at least the thousandth time.
He had learned all that he could, and then learned even more. In the ways of the Force, even the Emperor has openly admitted that Darth Vader has no equal. His connection to the energy of life is far too vast to keep in check, so he lets it run amok throughout the galaxy. At any time, especially when he doesn't actively utilize the Force, he can know what is happening within ten light years from his position. He has studied the records of the Old Republic, and of the time before that, the time when each of the different planets waged war with one another, and the Jedi fought the Sith with such ferocity that it made Palpatine's rise to power look like a tea party by comparison.
He gave up his passion, along with the rest of the emotions associated with it, a long time ago. On Mustafar, before he dueled his former mentor, choking the life out of Padmé. She had brought his fate to him, betrayed him, and he had repaid her for it. He has no regrets, and feels nothing for it. His dreams disagree, kicking and screaming at him to feel sorrow and repent, but his waking mind is serene and secure in its choice of action.
While Vader had very much been a free spirit in his youth, wild and rowdy, he had never truly been chaotic until the beginning of the Clone Wars. His love for Padmé had driven him to do strange and terrible things, cruel and unforgivable things, but that was fine with him. He did not ask for forgiveness, after all. Now, under the Empire, the galaxy is a united front. Rebellion is cut down and stomped out, leaving naught but a harmony of worlds.
There was, truly, no death. Death was relative, and yet nonexistent; when all things in the galaxy are made up of the Force, why should a change in the state of their matter mean anything? Furthermore, there were many who had come back from the netherworld of the Force as ghosts and apparitions. He understood perfectly that death was no more than a contrived illusion, and that the only truth of existence was existence itself: the Force.
Fear is the path to the Dark Side.
Fear leads to anger.
Anger leads to hate.
Hate leads to suffering.
Darth Vader did not fear, did not anger, did not hate...and yet he suffered. His pain was mighty, only outstripped by the power of the Force that he could feel inside of his body and mind. His pain was great enough to kill, to provoke, to shock and alert. The ocean of emotion, that surrounded the small island-fortress of his mind, was wrought with power if he accepted to give in to his emotions. He rejected it, however, because doing so would open him up to feeling even greater grief and sadness than one might think possible.
How utterly fascinating that he is the only one who might understand the eternal joke that is his life.