One of my favourite blog for children's writers is Mary Kole's Kidlit.com. Mary Kole is an associate agent at Andrea Brown Literary Agency. Quote from her post today:
It’s in your best interest to develop a thick skin, learn how to take criticism and rejection, separate yourself from what you’ve put on a page, learn everything you can about the industry, get realistic, and keep writing every day. The one-in-a-million publication stories are the ones you hear because they’re glamorous. Most people get published through the tears, snot, spilled coffee, midnight breakdowns and rare moments of joy that comprise a long time spent chasing a dream. It’s not terribly sexy, nor is it quick. But that’s how people make it and that’s the truth.
I strongly recommend writers to read the entire post (not just for kids' writers!) and browse her blog for valuable writing advice. You can also follow her on Twitter at @Kid_Lit.