It turns out there is now some very good science that explains the value, importance and function of mental rest. In particular the research relates to our ability to have insights, the 'aha' moment when something that didn't make sense suddenly changes. (There is also the idea of just giving overused circuits a rest, but I think the more interesting issue is around how we solve complex problems.) The research points to the idea of valuing a fresh mind, as this is the time we are more likely to be able to solve tough problems. Instead of valuing times when our minds are quiet, we tend to automatically fill it up with emails or every day challenges that waste a precious commodity.