Your attitude and your point-of-view determine how you see things and the way you see things determines to a large extent what you get out of life. Breakup with your girlfriend? You can have a negative attitude and think that you are not attractive, that you have no value, etc. or you can look at is as something that was inevitable and as an opportunity to move on. Get ill a lot? You can see it as God and nature punishing you for being a rotten person or you can see it as a warning that you need to change your lifestyle, exercise more, eat better, etc. Loose your job? You can see it as a rejection of you as a person and as a contributor to society and spend the rest of your life wallowing in pity or you can see it as an opportunity to get a better job, to go back to school, or to start a new career. (I've always found it both interesting and humorous that when a regular worker was told his services were no longer needed, the business that I worked for said he had been laid-off, but when a senior-level manager lost his position they were much more positive in announcing that, “VP of Sales, John Xxx has been granted an opportunity to further his career by joining another company.” which means exactly the same thing, they just say in in a much more positive way).  
    In quantum physics, they say that the observer changes the observed so when we look at something it is not really what we see because our observation has changed it.  What the physicists don't say is how our point-of-view effects how the observed thing changes.  I'm sure when studies are done on that, they will find
that attitude and point-of-view makes a big difference.
    Just as we have setbacks in the material world, things rarely go smoothly in our efforts to become spiritually enlightened. A positive attitude helps us overcome the obstacles and become stronger and continue on the path while a very negative, self-pitying one will cause us to quit.  So we need to examine ourselves regularly and try to keep reasonably positive.