How do you tell whether you’re being open to new opportunities or just being flighty?

As I was finishing the MVP of one project (Daily Thanks), there were multiple offshoot ideas I wanted to build. Rather than spend more time refining Daily Thanks, I started building out a project for landing page feedback (Indie Swarm).

I'm continuing to talk about and share the first project, so I don't feel like I'm falling into the trap of just building, but... Is this fast iteration smart? Making a mistake?

In general, how do you tell when you’re being open to new opportunities vs. just being flighty?

How much effort do you put into one project before spinning up another?