This was a neat way to put it. Goals have always bothered me because they are an excuse to stop working – either because they are fulfilled, or because it becomes clear they will not be fulfilled. Constraints don't have the same problem.
Goals have always been more like milestones to me and also something that you can change. I see goals and constraints both as different kind of tools to be used. If you decide to change direction, both of them can change.
Put this way (P and GP) this makes a lot more sense. Thank you, glad you chose to share!