Things happen
Positive thinking is not about believing everything that has happened is a Good Thing.
In fact, this type of thinking can be harmful. Pretending that everything is okay is simply denial. It is also a form of optimism that is disabling, because you are telling yourself that everything will work itself out eventually. If you're that positive, you're not going to get anything done. You have essentially resigned your power to take action for a mind-numbing belief or hallucination that everything will work out for the better - without your action.
The reason for the name then, is that positive thinkers can see the "light" in a Bad Situation. They will not regress from it, but they will not pretend nothing has happened. They will look for an opportunity again, and continue moving in a positive direction despite any setback!
This is a semantic dispute, but perhaps a better way to frame positive thinking is optimal thinking. A far more neutral term for a neutral approach on events. The optimal thinker does not distinguish between Good or Bad. To the optimal thinker, things happen. Then it will respond by adapting its approach towards its goal.
The thing has already happened. Don't mourn lost opportunities, just adapt and keep moving forward.
