Decide Whether to Write the Next Book or Return to an Unfinished One

Every writer eventually faces the abandoned project and the shiny new idea at the same time. The new idea always has more energy. The question is whether that energy is a signal or a symptom of the thing that stalled you last time. This looks at both projects, what you said you care about, and gives you a direct answer rather than permission to do whatever you were already going to do.

I have an unfinished creative project and a new idea competing for my attention. Help me decide which to pursue.

The unfinished project: [describe where it is, why it stalled, and what finishing it would require]
The new idea: [describe it and why it is pulling at you right now]
What I care about most as a writer: [describe, for example finishing things, commercial potential, personal meaning, craft development]

Tell me: what abandoning the unfinished project typically costs long-term (beyond this project), whether the new idea energy is a symptom of something or a genuine signal, and which choice better serves what I said I care about. Give me a clear recommendation rather than a framework for deciding.