Embrace Failure...but don't Accept Mediocrity.
As writers we struggle with our fears, the predominant one being that our writing sucks. Of course it sucks, all writing sucks. Until, it doesn't. When a painter begins with a blank canvas, his painting will be varying stages of ugly...until it's done. A sculptor will create things that others are unable to decipher...until the work is complete. These artists don't see the work as bad just because it's begun but not yet done.
WRITERS...don't hold yourselves to a higher standard than other artists.
Those words on the page are not the last words on the page and many of them will leave the page to be replaced by better words, and that's the point. Failure only leads to success if we allow the process to flow. Too often we grow impatient, and we seek to control the narrative, not the writing.
This is the road to mediocrity. When we accept short cuts or stereotypes or done to death tropes, we are accepting work that barely is, work that doesn't rise to expectations, ours or others. A story, like many things, must take place in its own time, not your's, not your agent's, not publishing's, not even the public's.
The next time a story isn't moving at the pace you'd like, step away. Write a poem, a short story, a song. Write an essay or a letter. Give your narrative time to become what it will be, what it must be, and more importantly, allow it to be in its own time.