Giving up a goal

I am struggling to decide if a goal is really worth continuing to work towards. I have invested a lot of time and energy in attempting to achieve the goal. My enthusiasm was high initially because it was exciting and audacious. Now, though, my work towards that specific goal keeps getting placed on the back burner. I don’t know if I am thinking of letting it go because it’s hard or because it is not how I want my future to be. How do we know when to pivot or keep pushing?