Startups rarely get in trouble because the upside happens but they quickly do when downside happens. Entrepreneurs do not spend time worrying about potential downsides. They always worry about how to make upside happen.
It would serve entreprenurs well if they were to worry about things that may go wrong. What would happen if a key engineer left? If the expected large order failed to materialize? There is a endlist list of things that can go wrong. Some contigency planning to avert these would serve the entreprenur well if they were come to pass.
Unlike large companies, startups dont have resources to have redundancies. So they have to be extra alert to see the trouble looming a mile away. Entreprenurs should only take on the risks they have to. Any avoidable risk should be avoided.
More often than not success depends on eliminating all potetial causes of failures. They should especially ask when things are looking up, what am I missing?