When you have a big enough retirement account, you have the option to continue working only if you want to.
Although the time constraints aren't as stringent in a business setting, the entrepreneur must develop the trait of resilience and mental toughness to continue on despite failure and disappointment again and again.
The hardest (and most expensive) sale you will ever make is the first one.
With social media, news travels very fast. When a customer has bad experiences, the news can become viral and destroy a business.