Sometimes
you don't need a plan, and can just make it up as you go. In other cases, a
rough plan will be good enough, and for some goals, you will need a very
detailed plan.
For a
complex creative goal, like building a house or a business, it's essential to
have a detailed plan. It almost certainly won't unfold exactly that way, for as
the saying goes: “No battle plan survives contact with the enemy” – but it
clarifies your idea, builds your belief in a successful outcome, and is useful
for communicating your idea to others so they can get involved.
If you can't
conceive of a plan for how to get all the way to your goal, simply plan how to
get to the first milestone and trust that things will seem clearer from there.