Consider a man building a log cabin.
As he scours the forest for suitable trees, his vision of the finished product will guide him. He will know when a log he is considering is too long, too short, too thin, too thick, or just right.
If he didn't have the goal of a certain floor plan and a certain layout in his mind, he would wander the woods aimlessly, cutting down trees at random. When he finished harvesting trees he would have a hodgepodge of different sizes, shapes, qualities, and even colors. He could be a great lumberjack, a master at the craft of cutting down trees and de-limbing them. However, if he doesn't have a goal in mind, the end result will be chaos: a random assortment of various types, lengths, colors, and shapes of logs. Hardly the stuff out of which his log cabin could be built.
Consciously pursuing a goal will provide guidance when you come to a fork in the road. Just as our cabin builder is guided as to which trees to select and which trees to leave because he has a view of the finished product, so too you will know what route to take because you will be guided by your vision; your goal.
Keeping your goal in mind will help illuminate the path you should take when you're unclear.
It will help you to determine the correct route for you to take when there are several routes that all seem equally appealing. It will clear up any questions in your mind. You will know what path to choose because you will know what your end goal is.
Let's look at the illustration of the cabin builder from another angle. Chopping down trees is hard work. Removing the limbs and dragging them through the forest to your building site is even harder.
If our friend does not have a vision of his end result, he will be quite likely to quit when he gets tired.
Perhaps in the morning he will set out zealously — chopping trees with gusto. Yet, as the day wears on and the sun begins to beat down on him, if he doesn't have a purpose in what he is doing, he will quit. And rightfully so: What kind of an idiot would chop trees down in the blazing sun just to do it? If he doesn't have the picture of the end product in mind — if he doesn't have the vision of his goal — then he will quit when the road gets tough.
Likewise, if you keep your goal foremost in your mind, it will keep you going when you want to quit.
You will have a reason to keep going. You will be like our friend who chops trees not because he needs something to keep him occupied, but because he has his goal in mind.