I will be bad at writing
I have about 10 dead blog posts on my hard drive at this point. I've been writing these for a while and haven't posted anything.
I think the problem is that, growing up, you are taught to be good at things. It's important to be good at things, but worst is to be bad at something you don't have to do, but to keep being bad at it anyway. To do something and be bad at it by choice is pretentious. It implies you think you are better than you are, because why else would you be doing this thing in public?
So to ward off this fear I'm going to start by saying that I intend to be bad at writing and to post my terrible writing on my blog. It will probably be pretentious, it will probably be trying to hard, but I'll get better.
And someone once said, when encouraging me to post my writing publicly, it's not like anyone will read it.