Why do I write?

Reading has always been an essential part of my life, therefore my inspiration must be  linked to the desire of one day having a positive effect on someone, anyone,  just as my favourite authors have had on me.  Otherwise, I don't walk around with a notebook where I jot down feelings or describe landscapes or random situations - I wish I did!  I also wish I were self-disciplined enough to write on a regular basis.  I'm embarrassed to say that I've been relying on people challenging and egging me on: 'write a story for someone who's afraid of...' - And I do it, no problem.   (cf. http://thoughts-dreams-tales.blogspot.com.es/2015/07/sophia-meets-fireman-oscar.html)  
I think about the topic, read about the phobia or whatever the subject is about and I sleep on it.  Before I actually sit down and write something I've already come up with many possible storylines, scenarios, etc...Next, I write the first draft on a piece of paper (which I'd never show anyone out of sheer embarrassment) and which is torn as soon as the text is copied onto a word document; the fear of someone finding and reading that first draft outweighs the pity felt for the deformed notebook. As I'm typing the text, I'm actually rewriting and editing the story.  Then I make some more changes until reason tells me it's time to stop.  So I stop.  In short, once I have a writing topic (or challenge) I read non-fiction books/articles in some way related to the topic and rely on the power of thought and, especially, dreams, where I can have as many takes as I need.  Finally, there are some posts that hit a nerve and compel me to write.  This comment is actually part of a comment I left on one such post about «inspiration». (http://daniellestejust.blogspot.com.es) 

And you?  What triggers your need to write?