I would never advise someone to write to the market, but I do think there is wisdom in writing away from the market. If there is a field that is really really saturated right now, maybe not a good time to start that new idea you have for that field. These things are cyclical and trends don't last forever, so you can always return to it later when it will feel more fresh. Of course that's not a hard and fast rule, but if you're trying to decide where to put your energy next it's something to consider.