One of the hardest things about being a writer, for me, is self-discipline. If I'm not feeling positive about what I'm writing, I will find every reason to not sit down to write. And of course, this frustrates me because I have a long list of books/stories I want to complete and avoiding writing is the last thing I should be doing.
I think this is typical of most writers. Although I've heard other writers recommend that you sit down at your computer and eventually something will come out so that you should just write every day, I do want to focus, in particular, on the stories I have in me. I usually avoid the 'practice' sessions that I see in various writer magazines because it isn't that I have no ideas to write about, if possible, I may have too many. I just need to fill in the stories that I have in me faster.
Confidence, too, is a block for me. I don't know if I have that in common with other writers. I think some might get a little praise that goes right to their heads and are over-confident of their ability to write a good story. There is so much more than putting a story down on paper and I tend to get bogged down in the syntax and rules in writing a great piece of fiction. But that is only because I want to write a great work of fiction.
And then once you start submitting your work, well, when it comes right down to it, I guess this might be the hardest thing about being a writer. Because you want people to like the work that just poured out of you through your heart and soul, you can be overly sensitive to rejection. I guess the best advice here really is to not take it as a personal rejection. I know, easy for me to say and wouldn't it be fabulous if I believed this! But maybe try to take it as a sign that the publication you submitted to, not even the entire publication but perhaps the one person who read it, didn't like your story. But someone else might. And you just have to keep submitting until you find the right place. Think about J.K. Rowling and Stephen King who have a combined total of 42 rejections! And they both eventually found their publishers and both went on to great success.