Single Aim

One student asked a professor. I have many interests, but I cannot select one to be my sole interest.
The professor answered, you must select one to be your interest, then you should spend your time on this aim.
In this human world, somebody are successful, some fail. It is because, someone invest time and energy on their single aim. They success.
Many people spend their time and energy on the thing without aim. They just do things aimlessly, never persist on one thing to the end. They fail.
It is true that many people only do things without regularity, day in, day out, no planning. Finally, they achieve nothing.
But, time does not wait for you. Time is your life, when your life is away, what you can do for your aim?
In this world there is no easy things but also no difficult things. It depends on what you do and struggle. Success belongs to those who worked hard.