Dive In...The Water's Great
If you judge a fish by its ability to climb a tree,
it will live its whole life believing that it is stupid.
~ Albert Einstein
And if you judge your writing compared to other great writers, you just might feel like that fish. Yes, there is much to be said for studying great writing and striving for that kind of achievement with your own prose... But there's a huge difference between that and sinking into the mire of I-suck-and-I'm-an-idiot-to-think-I-can-write depression.
There's only one you, and no one can write like you. God made you exactly the way you are for a purpose. You write the way you do because it's the way God wants you to write. Believing your writing is stupid is akin to looking God in the face and saying, "Hey, you made me wrong."
Do you really want to say that to the living God?
I didn't think so. So whip out that pen and let the words flow. Swim, little fishy. Swim.