"Concentrate all your thoughts upon the work at hand". The sun rays do not burn until brought to focus" -Alexander Graham Bell
Concentration is the lap on which attention rests. When you are focused on a particular dream at a particular time, you are able to give it all your thoughts, energy, action, and attention.
To be in focus means to direct all your scattered powers to a common channel and guess how concentrated that group of powers will be.
You can't reach an optimum level of your dreams when you always give them a divided attention. Perhaps, you are not sure if it will succeed, so you are thinking of "trial and error". That can't be the best choice of behaviour.
Lack of focus is the major cause of unfinished tasks, neglected tasks and poorly done jobs. It also delays your time and makes you late.
Stay focused; don't be distracted away from your goals... You will be there by the grace of God!