A goal on its own changes very little. What changes behaviour is the chain of small actions you set up to support it, repeated often enough that they stop needing a decision.
Here's the honest arithmetic: if a goal needs a weekly action and you do it most weeks, you've completed the bulk of the work by the end of a few months. Skip most weeks, and the goal just sits there unchanged, no matter how clearly you wrote it down.
The gap between people who reach a goal and people who don't is rarely about how big the goal was. It's about whether the actions underneath it were small enough to repeat without a fight.
That's good news, actually. It means the goal itself isn't the problem you need to fix - the system supporting it is, and systems are far easier to redesign than willpower is to summon.