Not if that daydreaming leads the mind to unblock thoughts that seem to clam up when confronted by a blank commuter screen. Sometimes we can think too hard and try to force a story to leap onto the screen. But there's nothing more unproductive than staring at a blank computer screen - far better then, to stare into space - daydream a bit, go and do something completely different, or go and do nothing at all... sneak up on an idea when it least expects it, then round it up into a corner of your mind where you can find it again next time you have a pen or computer to hand.
Some of my best ideas or problem solutions have come to me when they can see I have no pen to hand - the swimming pool is a good one. There's something about swimming up and down the length of a swimming pool that clears the mind.
A new and unexpected one is a hay barn - filling hay nets for my daughter's horse - and then she wonders why it takes me so long... but where's the rush?
Some of my best ideas unravel whilst watching the cats play in the garden, now all I have to do is figure out how to carry on typing with a cat clambering about on my shoulders, or trying to help with the typing...