belief.

The word often gets a bad rap because, some will say, it doesn't matter what we believe. It matters what we do. 

And that is true. But, what we do is dependent on what we believe. 

We don't do anything in life unless we believe there is a higher chance of a potentially good outcome than a potentially bad outcome. 

Good and bad are very subjective terms but whatever those mean to an individual, and their belief, will determine their action. 

I don't drive 200 mph on the freeway. I believe the odds of a negative outcome outweigh the positive. 

Sometimes our beliefs are correct. Sometimes they are not. Sometimes our beliefs of positive and negative are correct, sometimes they are not. 

Why are you not writing that book? Making that film? Starting that blog? Quitting your job? Opening that restaurant?