Everyone dissociates; it's what happens when you're not "here" because you're thinking of something else (as you describe) or when you're reading a book and involved in the action instead of paying attention to your mother calling you for dinner or to fold the laundry (which I'd get in trouble for because she'd have to tell me multiple times :-)

You can only put your attention one place at a time; even so-called "multi-taskers" are really only doing one thing at a time but changing often/quickly between tasks like those circus performers that get a zillion plates spinning at once? And, you can choose where to put your attention.

I have trouble kind of like you describe, where I say goodbye to someone but other people are saying goodbye, etc. and I just kind of drift off, not paying attention to the continuing chit chat while everyone gets out the door. It's a form of "boredom" and literally not "caring." I think that happens more than people like to admit, where they drift off because whatever is happening is less compelling than what they're thinking or thinking at all/concentrating is less compelling than just going "blank" and paying attention to nothing. If it was dark in your hallway and no one else was around and you couldn't think of much interesting to think about; that would be a kind of deprivation of stimulation of sorts I think, and not much would be going on anywhere?

We have to train our minds (because we want to) to pay attention to something in particular. If you want friends, you have to pay attention to them/people around you and make the effort to enter into conversations, etc. Sometimes, especially when I was a teenager, I didn't like doing something so I'd "avoid" it by my inattention. Well, that gets to be a habit (like anything else) and you get better at not paying attention! That's not a good thing?

One can't "stand still" one is always moving forward or backwards; that's why it's is best to work hard especially when depressed or having a hard time of any sort to keep trying because otherwise the "speed" at which one falls backwards will increase and the further "back" you are the harder it is to get moving forward again and make up the "distance." Think about subjects you have trouble with in school and when that started and how you have behaved since you started having trouble?

I have trouble with computer programming because I didn't pay attention and work very hard at math in high school so didn't get the right/enough algebra because my high school math problems led to me ducking out and taking the easiest college math classes I could. I was supposed to take calculus but took the polyglot basic math instead: http://www.math.umd.edu/undergraduat...sMATH110.shtml

We don't know what we're going to need in the future so paying attention so we "collect" what we can as it goes by is a good idea I think. I spent 10-20 years in my head in the 1960's and 70's and didn't learn a darn thing "new"/helpful other than that was a bad idea :-) I'd love to have that time back now!