Thinking about what you have is a way to look at things in positive way.
 You focus on what you have instead of what you do not have.
 That way you would feel very proud of yourself because you have done a good job of getting it.
 It motivates you to work harder so that you will be able to acquire more work done or personal belongings.
 It also means thinking about what you have accomplished before you reach your goal, instead of thinking about your goal or from your goal.
 This way you feel confidence that you reach your goal in the future.
 It motivates you to work harder.
 You are eager to get down dirty and work some more toward your goal.
 It is a positive feedback that encourages you to strive some more.
In the opposite, you focus on what you do not have.
 It is a negative attitude.
 It discourages you and makes you feel like a loser.
 You have no energy to move forward.
 You feel upset with yourself because of this negative thought.
 You blame yourself for not having the ability to reach your goal.
 You give up your goal completely.
 For example, keeping up with Joneses is a waste of time because you concentrate on making more money in order to fulfill your life style as your group of friends.
 You exhaust your mental and physical energy.
You may get into trouble because you did illegal act to get your hands on money.
 Focusing on what you do not have may ruin your life.
 Moreover, focusing on what you do not have may stress you out.
 It can make you getting sick such as heart attack, high blood pressure, and amnesia.
 Totally, it ruins your health, your family, and your life.