Whenever that happens to me that something goes so quickly, I suspect a muse had helped me. Do you know your muse?
Yes, at least I think I know her.
She is a part of me who moves in mysterious ways.
Often times, I am, too easily distracted, then she will flee for a time. She is active in Summer months. Music is a great inducer for her to become active and seductive, reading another bards work is also good for her.
Often times, I will read my own work and the spark will zing, then we write.