Where do dreams come from?

Its quite normal for me to wake up in the middle of the night (after just about a couple of hours of sleep) and find my brain working overtime! No matter what time of the day it is... the first thing I try to recall as I wake up is... what did I dream about? Had read it somewhere that if you try to recall your dreams first thing in the morning... the chances of you remembering them are higher!
This morning when I woke up (ok... I'm not talking about right now... its still midnight in my sleep cycle... or rather early evening... I'm talking about getting up at 3pm on the 22nd of September)... I had a big smile on my face till I remembered my dream. I had had some ghastly nightmare about snakes... and those who know me know that I'm shit scared of them...(Ophiophobia... GRE vocab did help somewhere!) Now I know where that dream came from... Lately every damn channel has been playing the trailer of "Snakes on a Plane" and no matter how hard I try I can't seem to miss seeing it... Now that is some tv which should come with a warning!
But its not these dreams that are a puzzle to me right now... I have figured out that most of my nightmares (as well as the good dreams) come out of stuff that I have read over the past few days... or discussed with pepole... or seen on tv! Nah... I'm talking about the dreams and the aspirations... the goals of my life.. where did they come from?
I have a big meeting tomorrow and I know one of the first questions is going to be "What are your future plans? Why do you want to do product design?" I'm trying to figure out a good answer... (I need it for my SOP too!) So i thought... well... lets try to find out where it all started? When did I decide that I wanna do Product Design? After a lot of sleepless nights I have narrowed that down to sometime while I was doing my practical training at Delhi! "Wow! Was the place so good?" Actually... I hate to say this... but it was what I did not learn at the office that taught me what I wanted... and it was what I did there that made me realise that this is not the kind of life I wanna lead... (No offence to JRA here... I did some top notch work which are going to be the key slides of my portfolio!) The next question is most obviously going to be - "Why did you do architecture then?" I remember the juror who came to grade us on our practical training telling me that I had wasted a seat in the college... and that someone who really wanted to do architecture could have been studying there instead of me! I was quite upset then... it lasted for a couple of days after which I said "Bullshit! Design is design and I deserve to be here!"
But we are digressing here... I was supposed to be writing about my dreams... and these are just paths to achieving it... I know "architecture just happened"... there was no guiding light or highlighted letters telling me that this is what I want to do... But a person cannot live without a purpose for very long... (well.. atleast I cannot!)... So somewhere along the line I had to sit down and actually think about what I wanted to do in life... I had done journalism for 45 days before shifting to architecture... Media fascinated me... but so did architecture and products... Now what do these things have in common? Why do I like them? What attracted me to them? Yes.. there is creativity involved on all three... but more than that... its about communication... be it written or visual... people use these to express themselves... and what do I want to do? I want to design these statements! This design could be for a person, a company or even a country... but I want every design of mine to reflect the experience and express the dreams! And that is what I want to learn... "Where do dreams come from?"