What about "when faced with a hard problem, close your eyes, clear your mind and focus your attention for a few minutes to the issue at hand"?

It sounds so very simple, that I routinely fail to do it when, e.g. I try to solve some project euler problem or another, and I don't see a solution in the first few seconds, do something else for a while, until I finally get a handle on my slippery mind, sit down and solve the bloody thing.