Step away and take some time off - that's always the best way. I also always planned my holiday baking (in my shop) in such a way that designs were detemined in advance of the rush, and so not every order was customized. It's very tough to be constantly designing when you really need to be in production mode (esp. at key money-making times of the year). Easier said than done though . . . I don't often take my own advice, and so I am usually teetering on the edge of burn-out.