When a minor character takes on a life of their own and their subplot adds depth to your overall story. Wes and Stan do this in my work. They start off as mischievous sprites. Wes becomes brave and discovers a side to himself he never knew he had. Stan learns not to take things at face value.
Completing a story, particularly a novel. It is an achievement.
When the one-liner doesn’t work as well as you’d hoped!
Having to take a out a minor character because they don’t develop the plot. And if any character doesn’t advance your story, you have to kill your darlings. Better that than allow such characters to kill your story with boredom.
When you think you’ll never finish the tale!
Not being able to get the words out quickly enough when the inspiration really flows.
Spell checkers! Use a decent dictionary. Why are UK computers programmed to have the US dictionary as first option? I’ve nothing against the Americans but we have our own spellings (the right ones and I only say that because we gave the world Shakespeare, Dickens and Austen!).