I've known many writers who are afraid to submit their work to an editor. Oh, many of them don't actually speak those words I'm afraid to send my work to an editor. but it's what is running through their mind, maybe even subconsciously. So, they make up excuses as to why they haven't submitted any of the many finished pieces in their files.
They claim they don't have time, or they haven't found the right market yet. Or they'll fool themselves by saying they'll work on it next month because there are too many things going on in their life right now. All of those may be quite valid reasons but it's often a cover-up for the real reason. They're afraid.
That's nothing to be ashamed of, but it is something to work on. I'm the first one to agree that exposing your precious words to the world is filled with risk. The greatest risk being that you'll not only be rejected but also get a scathing rejection letter. They hurt! Darned right they do. But guess what? Maybe the editor will love what you sent, and it will end up being published. Happiness.
But that can also be a frightening event. Only in the sense that once published, it's gong to be expected that you keep producing good material. You can and will, but you'll also write things that are going to get that rejection letter, too. It's all a part of this writing game we play.
So, how do you overcome the fear to send your work for other eyes to see? I think it comes down to an attitude adjustment. Have a chat with yourself. A writer needs to develop a tough hide so that the arrows of rejection can't penetrate. You'll never get to the point where it doesn't affect you in some way, but you can become hardened enough to either send the piece out again or file it away for some revisons later.
As far as being afraid when your work has been accepted--what a wonderful problem to have. Someone liked your writing well enough to publish it and pay for it. Rise to the occasion and keep on writing. You did it once, and you can do it again.