Writing, for the most part, is not about beginnings and endings. Middles form the majority of the work: adding, substituting and deleting words in an attempt to achieve the right pace/emotion/description/whatever. Writing middles holds neither the refreshment of beginnings nor the satisfaction of endings. Doubts don't creep in - they gush in a deluge that overwhelms.
I'm currently reading Bird by Bird by Annie Lamott. It's helping me to stay motivated and feel uplifted. The title comes from an anecdote Lamott tells about her brother, who left a school report on birds until the day before it was due. As he sat too overwhemed by his task to make any progress, his father told him to take it bird by bird. That's what I'm trying to do.
Under the umbrella term 'middles' comes 'middle drafts'. These are the drafts that come between the first draft, which usually involves mammoth changes, and the minimal tweaking of the final draft. I'm currently working on three short stories in this stage. Middle drafts are tricky because it's diffcult to maintain a sense of perspective. Many of the changes I make are reversed in the next draft. Often, it can feel like a waste of time.
But this experimentation is necessary. Finding out what doesn't work benefits both the individual story and my development as a writer. Writing middles and middle drafts is a lonely task, but it's important to keep going. So that's what I'm doing: cracking on, bird by bird, word by word.