A thought often leads to an immediate notion or idea, like something seen in the fog. I usually fix my gaze on it and try to bring it into focus. Then, there is a slow process of the thought or thing becoming clear and then concrete.

At that point it feels like a Eureka moment and it’s really tempting to just pursue that one idea until it feels like you’re done with it. But, its a bit like starting at the end?!

You have to retain that original thought and keep coming back to it. It can get lost really easily. That is the impetus for the work and it is how you can measure whether the work is successful.
Like Tom said, the process must be divergent at the start and only converge at the end.