Successful people maintain a positive focus in life no matter what is going on around them. They stay focused on their past successes rather than their past failures, and on the next action steps they need to take to get them closer to the fulfillment of their goals rather than all the other distractions that life presents to them.
On a daily basis, I find this quote hard to remember and harder to live. However, looking back, the times in my life that were the most successful, and where things seemed to just happen were the times where I worked hard to maintain my positive focus. The effort is definitely worth it!