The author Logan Pearsall Smith said: "Every author, however modest, keeps a most outrageous vanity chained like a madman in the padded cell of his breast." I love that.
As a person, I have pretty healthy self-esteem, self-confidence, self-respect, etc. I can do a lot of neat stuff, I'm intelligent, and so on. It takes a lot to shake that for me--I tend to live on a pretty even keel of self-acceptance.
As a writer, however, I tend to vascillate between three points. One one end is my "padded cell", the times I'm convinced I'm Ernest Hemingway, Raymond Chandler, and Patrick O'Brian all in one. The literary equivalant of combining Joss Whedon, Peter Jackson, Baz Luhrman, and M. Night Shyamalan.
On the other end of the spectrum lie the "doldrums". I can get stuck for days there, convinced I'm the worst writer in the history of mankind. This usually happens when I'm out of ideas--I drift along, slack-sailed, until another idea eventually wafts my way.
In the middle is reality. I'm there most of the time--I know I'm better than some writers, but not spectacular, by any means.
Oh, and I got in 2,728 words last night...I'm up to 16,235 now!