"Obstacles are those frightful things you see when you take your eyes off your goals," What does this quote mean and what is the importance of it?

What this quote means is that you only see things as obstacles (as problems) when you take your eye off the goal that you are trying to reach.  When you are focused on the goal, you do not worry about what is between you and that goal.  Instead, you just concentrate on the goal and take whatever is between you and that goal in your stride.

This is one of those motivational type of quotes -- that is its importance.  It is meant to remind us not to get too bogged down worrying about what we have to overcome each day.  Instead, we should concentrate on our goals --that will make us more successful.