How Come?

How come, once I turn the computer off, I can come up with witty, enlightening, relavent posts.. but once the computer is switched back on, the mere act of pressing the "on" button, causes a memory dump.. and I sit there looking at the blank screen with an equally blank brain? Then once again "off".. engaged in meaningless tasks and the mind floods with ideas.. and of course I'm out of reach of a keyboard so the thoughts flow over and out my brain.. never to be found again.. such is life.