Bill Gates is a 'rational optimist' – and maybe you should be too

• Bill Gates has found the perfect balance between optimism and pessimism, says Morgan Housel.
• This approach can be applied to any field of life, the psychologist writes in a new book.
• The Microsoft cofounder also seems to be demonstrating "rational optimism" when it comes to AI. 

Why has Bill Gates been so successful? One psychologist and money expert thinks it's because the Microsoft cofounder is able to strike the perfect balance between optimism and pessimism.