Focus is a skill, which means that you can practice it, and strengthen it.
The first thing to do is to determine what you want, and write it down.
Once you write down your goal, and, there are many different tools designed to help you do this, you will have a destination to focus on.
You will wander, stray, or get lost at times.
But, with your goal on paper, you will always have a point towards which to re-orient.