Location: My office in Kuwait Music: Rot V2.0 (Extended) by SITD
I think one of the signs of 'design fatigue' is the temptation to toss everything plus the kitchen sink into your project. You know what I'm talking about. if you don't, here's a bit of help. Design fatigue results in that campaign setting that features tiefling ninjas riding dinosaurs OR cowboy robots from the Civil War that uses hex magic from the Vodoun Book of the Dead Names.
(Either that, or the designers have questionable taste. Or, maybe they've just found a niche I'm not willing to explore. I don't know).
What I do know is this; design fatigue = burnout. To get past this, you need to take time away from your project and to space out. I like getting the occasional massage, which I think clears and refreshes the mind. I also think immersing yourself in physical activities (I like swimming laps) is a good method for tuning out. I think staying away from the cerebral realms designers tend to enjoy (including various forms of media) is just solid advice. Get out, have a walk, play with your dog, or enjoy some iced tea in the park. But get out and move.
I'm not sure about other writers/designers, but sitting behind these screens all day can't be good for us.