Writer

I seem to have two states of being: the one where I'm writing on paper/computer, and the one where I'm writing in my head. Lately I sit and jot down a few ideas and stare at the screen and lose all interest in continuing my thoughts. But they are there and numerous - a veritable jungle of thoughts, overgrown, one tangling into another forming this mass of confused, yet interconnected ideas and feelings. Thoughts about me, love, my family, my relationships, my career, music, science, food, silence, movement. Where am I going? Who am I doing it with? Am I happy? All of this stuff whirling around in my head, coming out in sentence after sentence I formulate in my mind and that disappear by the time I sit down to put them on paper. When I'm driving, running, picking up milk at the supermarket, I am writing, writing, writing, only the words never become concrete.
Are those moments meant to be captured? Are they merely a warm up for my brain as it gets ready to send my fingers scribbling with a pen over paper or tapping on a keyboard? Is scripting imaginary conversations between characters and lovers or creating paragraphs on ideas as I read the newspaper or listen to the radio just a form of therapy for me or is it exercise that I do because writing is all that I really ever do and have done even when I cannot put one letter on a page?