How does the idea of karma, or ultimate justice, effect the way you behave?

I recently reread a book called *A New Earth* by Ekhart Tolle, and he has a whole chapter on how he believes there is no justice on this earth. There is plenty of examples to back this up, and he even goes so far as to say that this place is the opposite of utopia. He says this place is to help us on the journey of spiritual awareness, not here to make us happy. He then goes on to say that the universe is completely just and fair, and that justice will be served by the universe. Thus the reason he believes in Karma.<br><br>My question is, how does the idea of ultimate justice and karma effect the way you behave? <br><br>For instance, I know that as long as I am being a good person, that I will earn good karma and bad things that happen to me were probably the result of something I did in the past. Yes, external factors may have been at play, but maybe this is the universe's way of getting me to see myself and change for the better. Because of this, I try and have a positive attitude and know that everything is happening for a reason.<br><br>I know for a fact that if I didn't have this mindset, I would grow very bitter and angry at the world. This mindset was particularly helpful as I went through some major spiritual awakenings and loss of some of my biggest attachments. <br><br>So I guess my question is, do you believe in karma? And if so, does that change how you treat people and how you react to difficult situations?