Why is it that the best ideas come when unprepared?

  Why is it that my best book ideas hit me while driving or falling asleep? It is frustrating and though I have been able to jot things down every now and then, the majority of the time I spend the next morning dissecting the jumble of dreams to get at the wandering thoughts that so closely preceded them or when arriving at my destination wildly searching for pen and paper even as the ideas seep into my memory vaults, to be opened only at specific and ultimately unknown times…


  Anyone else ever experience this? How did you combat it? I have taken to carrying 5x7 cards with me during the day and having a pen or two around in case something strikes me.