Focus is keeping the result or prize in your sight. Focus has just as much to do with those things that you pay attention to as the things you choose to ignore.
For instance, if you allow negative outside influences to draw your focus away, you will have a difficult time reaching your goals.
Focus on your goals and desires, keep your energy moving in a direction that is in line with reaching these objectives.
The more you allow outside influences to draw that focus away from your goals, more of your energy and attention get used on these items.
Ultimately, it leaves less willpower and drive to be used for your true desires. If you can recognize those things that break your focus, you can begin to eliminate the source of the problem. If certain people break your focus than you must protect your mind from these influences, either by time spent or conversation topic.
You are in total control of what you focus on. Determine what you want and stay focused.