I write a lot of poetry , I write a few short stories , and without writing them down I even play song lyrics out in my head . The problem though is that I drive a lot too ! So I find that just every once in a while something passes through my mind and I say " I should stop and write that line down on paper " and I think , Oh I'll remember that one and kaboom ! It's gone forever !.......ArrrrrrH !
Problem solved: A voice recorder of some type. Creative people like you must catch your brilliant ideas by recording them as they emerge and form in your mind. OKAY? Stop losing your thoughts! I think a good ol' tape cassette recorder works best. Many musicians are still using these very handy old school devices. Get a good supply of batteries and keep one in yer car.
Well at home you should always keep a journal for jotting down ideas that inspire but of course not when you are driving. When driving you might thing of getting a small dictator or something that you can quickly turn on and then record your ideas. I know that when inspiration strikes me if I don't get my ideas written down somewhere then later forget it.