Positive thinking does not come naturally to many people. In fact, for most of us, the first thing that comes to mind whenever we encounter challenges are negative thoughts.
We think about what has happened, and then we think about who is to blame for the things that have gone wrong. Maybe your first instinct is to complain about things, to lash out at other people instead of looking at what you yourself have done. Ask yourself if you want to be around people like that. People who are so negative, they basically drag down everyone around them.
With negativity practically oozing out of their pores, I bet you wouldn't want to be around these people. So, don't be one of them. You have to make a conscious effort to direct your thoughts from the negative to the positive. It's hard if you're just starting out, but with enough time and practice, you'll find yourself thinking positive most of the time.