Young and inexperienced, I once started stories and quickly put down 5-10,000 words (17-35 pages). I would next wonder where to go and how to get there.
Starting a story now might take a month or more to produce 5,000 words. The difference?
Production and enthusiasm depend upon the story, whether the setting, story or character may be emphasized, and how the writer (I) feel about any of it. But the primary difference is in the author’s (my) outlook. Enthusiasm and impulse remain the same today as it was, but I am more deliberate: I know it will be a slog, write every damn word about every perceived point covering each conceivable concept. The first draft is the one time the author has the opportunity to take this overall view: think freely and make every expression idiotic, moronic or nonsensical as well as completely, profound and experimental.
All later work pares the manuscript by rewriting within the parameters of the givens of the story; next comes editing and proofreading.
The slower launch today may mean energy is not marshaled; doubts linger about the quality of the plot and confidence might be fleeting. But confidence will build throughout a writing, doing 1,000 or 2,000 words a day, and feeling content having produced 20,000 words, 50,000 words, a first draft, and the next draft. It is that build of confidence, a building of ego, which allows a writer to finish a writing.