Being a writer takes a lot of discernment about the kinds of people you let into your creative process. I can’t imagine being a writer without friends to read my writing.
Allies are people who make you feel confident. They are your friends, first. They want good things for you. They, like you, are on “team better world.” They are honest but never mean. This doesn’t mean they are always nice for the sake of being nice, or don’t offer criticism. But their criticism is always constructive.
Unfortunately, there are some competitive writers out there who want us to feel bad about our writing so they can feel better about their own. Learn to spot them. Put them on a list of writing enemies. Don’t let them go near your work. That doesn’t mean they are your enemies though. You can still grab a beer with them from time to time. They just don’t get to be your writing ally.
Your new writing project is a newborn child. You’re not going to let just anyone hold it. No one has the right to tell you to kill your newborn child.
Also, ask yourself if you are a constructive critic when someone asks you to read their work. Are you generous while you read? Assume that there is something good about what you’re reading and look for it. Then try to spot what’s getting in the way. You wouldn’t publish it because … but you would publish it if …
Make a list: who can you trust with your writing? Who brings confidence to your work, wants you to write the best you can possibly write because, well, they like you?
Nora Bonner 
I sense a theme going here…:-).
Most of these ideas come from my conversations. Thanks for helping me come up with this one. 🙂