The outer world is a mere reflection of your inner self. When you feel love within, you see love outside. When you have anger within, you feel mistrust outside. The inner reality spills outside. There is only 1 reality - the reality within you, your values, your feelings.
Often, we wish the outer world to change. But for the outside change to happen, it must 1st start inside. Once your inner reality matches the outer aspiration, then you will see the change automatically.
Therefore, we say that, "the world changes from within".