Bill Gates didn't consider himself successful even 11 years after becoming a billionaire. According to him, it wasn't until 1998, when Microsoft was already worth $250 billion and dominated the market thanks to Windows 95, that he first felt that the company could afford to make mistakes and still survive

Before that, Gates lived in a state of constant fear, working 80 hours a week and thinking that any mistake could destroy Microsoft. He was so focused on the company's growth that he didn't even celebrate its anniversaries, believing that there was no time to celebrate.

Now that Microsoft is valued at more than $3 trillion and his personal fortune exceeds $165 billion, Gates admits that being overly obsessed with success can be destructive - both for business and for his personal life.