When you read the title of this post, you'll most likely think to yourself, "how can stress and relaxation go together?" To that I say think about the following.
Ever wonder why you've been racking your brains for ages to think of an idea for something or to remember something and it never happens? That is the stress bit. And then this idea comes to you perhaps when on a train or walking down the road or often when sat on the toilet (I'm sure you can admit to many a great idea happening in the loo). Well, during these moments is when you are likely to have been in some form of relaxation. See how the two work together?
Your mind is obviously in a stressful state and constantly forcing itself to find a solution which isn't usually a helpful process. The best solutions come when there is less pressure on your mind. This is the theory I'm subscribing to anyway.
But give it a go. Next time you're struggling with an essay or making something creative, take a break from it and see how that works. I guess these kind of situations are why people often say about a problem that you should 'sleep on it'.
Makes sense to me.