"In life as in football, you won't go far, unless you know were goal spots are" 

~ Arnold H. Glasgow 

 

What this quote is saying is that you won't go as far as you think you will unless you know where you have reached the limit to your success. If you keep reaching for your goal and don't know where the limit is then you might not go as far. You should know when you have reached your goal. For example, like the quote says about the goalposts. You can't play football without one. You won't know where to score and it won't be a good game. Another example is a soccer net. You won't know where to kick the soccer ball to make a score. It won't be fun and you will look like a maniac not knowing where to score.