" In life as in football, you won't go far, unless you know where goalposts are"

 Arnold H. Glasgow

What this is saying is that just like in football you need to know where the goal posts are so you can achieve a goal because if you don't know where the goal post are then you won't be able to achieve or make a goal. In life its the same thing you need to know where you are heading to and what you want to achieve like you need to know what path are you going in or you're going to take so you can achieve this. Your goalposts in life are where and what you want to do. If you know what you're going to do and know where you want to achieve the goal then that is your goal post that's where you want to achieve your goal. It compares to football because if you don't know where you are scoring then you won't be able to acomplish your goal.