"I don't intend to bring any alcohol up here, and I don't think there will be any opportunity to get any before the snow flies." (1.66)
Jack thinks that by isolating himself from alcohol, he won't be able to drink. Sound logic, right? Well, not at the Overlook, who can make martinis and cocktail nuts, among other things, out of thin air.
Danny's answering shriek, then Wendy's shocked gasp as she came around them and saw the peculiar angle of Danny's forearm; no arm was meant to hang quite that way in the world of normal families. (3.8)
The breaking of Danny's arm is a factor in the family's isolation. It lingers in the near past, making it so that neither Jack nor Wendy can feel good about themselves. They feel cut off from the people in the world who don't hurt their children. The incident does not, though, isolate Danny from Jack, at least as far as Danny's concerned. He loves his father no matter what.
[…] when snow fell, getting out of here would not be a matter of an hour's drive to Sidewinder but a major operation" (10.29)
Wendy, like Jack, is actually aware of just how isolated the Overlook is. But their options, or what they imagine as their options, make even extreme isolation look good.
He was still an alcoholic, always would be, probably since Sophomore Class Night in high school when he had taken his first drink. (14.54)
Jack's alcoholism is a major part of his isolation. Even though he's recovering, he thinks about drinking all the time. When he was drinking, it isolated him from his family, his students, and his writing. His temper is the other big isolating factor, and his temper plagues him, drunk or not.
The actual act of writing made her immensely hopeful, not because she expected great things from the play, but because she her husband seemed to be slowly closing a huge door on a room full of monsters. (16.1)
Wendy thinks writing is the key to helping Jack come out of the isolation brought on by his temper, his drinking, but most of all by his childhood of abuse.
"Hello? This is Jack Torrance […]. My son here can't stop crying. Please send THE MEN INWHITE COATS to take him to the SANNY-TARIUM. He's LOST HIS MARBLES." (21.119)
Danny feels very isolated by his ability, especially when he's at the Overlook and he starts to see all sorts of crazy things. He's afraid if he breaks down and shows his torment, he'll be deemed insane and isolated in a psychiatric hospital.
He raised the radio up and brought it down, and it smashed on the floor […] (26.33)
When Jack breaks the radio after the phones have already gone out, he destroys the one thing besides the snowmobile which can link them to the Outside word. Interestingly, he does it completely in his sleep.
He flung the magneto as far out into the snow as he could. It went much further than it should have. (33.66)
This time Jack is under the evil influence of the storage shed (see "Setting" for more) and his conscious feeling that the Overlook is his last chance to repair his life. The magneto is crucial to the functioning of the snowmobile. When Jack tosses it, he cements their isolation.
Even with the volume turned up loud he thought he could still hear Daddy screaming at them and battering the pantry door like an animal in a zoo cage. (47.7)
When Jack is locked in the pantry, Danny's empathy with his dire isolation is touching and frightening at the same time. It makes us wonder if somehow, just somehow, it was Danny who lets Jack out, rather than Grady – but that's just too big of a stretch even in a book like The Shining.
Far down the road but coming toward them, coming upward […] was a chain of pearly lights. […] The long darkness was over. (57.82-57.89)
These are the novel's final lines, before the Epilogue, that is. The lights are the rescue crew that has decided to take Halloran seriously and go to the Overlook to check on the Torrances. The lights represent the break in isolation. They seem to end the book with a glimmer of hope.