CoolP wrote on Apr 23^rd, 2011 at 12:29am:

but when I see that my problem has some logical nature, I stop the thing and approach it on the next day or so, after sleeping some time. There are days where you don't see or get a thing although it's clearly there. Next day, fresh eyes and mind, easy to catch.

Spot on CoolP! If you get bogged down chasing a problem, you get flustered. Once you get flustered, you are bound to fail because you are no longer thinking clearly/rationally. Walk away, calm down, THEN come back and try again. Better yet, waiting until the next day (after a sleep) is a great idea. Like CoolP says. :)