Jack: Wendy, darling, light of my life, I'm not gonna hurt ya. You didn't let me finish my sentence. I said, I'm not gonna hurt ya, I'm just gonna bash your brains in. Gonna bash 'em right the f*ck in!
Jack Torrance: Wendy, let me explain something to you. Whenever you come in here and interrupt me, you're breaking my concentration. You're distracting me. And it will then take me time to get back to where I was. You understand?
Wendy Torrance: Yeah.
Jack Torrance: Now, we're going to make a new rule. When you come in here and you hear me typing [types], or whether you DON'T hear me typing, or whatever the FUCK you hear me doing, when I'm in here, it means that I am working. THAT means don't come in. Now, do you think you can handle that?
Wendy Torrance: Yeah.
Jack Torrance: Good. Now why don't you start right now and get the fuck out of here?
Wendy Torrance: Stay away from me.
Jack Torrance: Why?
Wendy Torrance: I just wanna go back to my room.
Jack Torrance: Why?
Wendy Torrance: Well, I'm very confused and I just need time to think things over.
Jack Torrance: You've had your whole fucking life to think things over.
What good's a few minutes more gonna do you now?
Jack Torrance: Are you out of your fucking mind?
Grady Twins: Come play with us Danny. For ever and ever and ever.
Jack Torrance: Heeere's Johnny!
Lloyd: Women. Can't live with them, can't live without them.
Jack Torrance: Words of wisdom, Lloyd, my man. Words of wisdom.
Jack Torrance: God, I'd give anything for a drink. I'd give my god-damned soul for just a glass of beer.
Lloyd: What will you be drinking, sir?
Jack Torrance: Hair of the dog that bit me, Lloyd.
Dick Halloran: They turned out to be completely unreliable assholes.
Danny Torrance: Redrum. Redrum. Redrum.
Jack Torrance: Little pigs. Little pigs. Let me come in. Now by the hair on your chinny chinny chin? Then, I'll huff, and I'll puff, and I'll blow your house in!
Jack Torrance: Here's Johnny!
Jack Torrance: Here's to five miserable months on the wagon, and all the irreparable harm it has caused me.
Answer: Effectively, Danny's shining is what brings the hotel to life. Because he has such an incredibly powerful shine about him, all these weird ghost things in the hotel are able to materialize and reveal themselves. These weird ghost things are always present to some degree, and those people with a small degree of shine get glimpses of them - like Dick Hallorann. (It's not quite made clear in the movie, but Dick saw the woman in room 237 in the book). However, Danny's shine is so great that he gives these forces enough life to appear to those without any shine, people like his father and mother. As it's the hotel that's slowly driving Jack crazy, and the hotel gets its power from Danny's shining, then I'd say there's definitely a connection between Jack's insanity and Danny's abilities. In the movie, it's not as clear as it is in the book, but Jack is effectively possessed by the hotel. He's not a flawed drunk with an anger problem who loses his mind because of isolation. He's a flawed drunk with an anger problem who's doing the best he can, until the forces of the hotel get inside his head and make him lose it.
If Danny's shining is what brings the hotel back to life, does this mean that all the previous "Jacks" had a son or daughter with the shining too?