If you have a career goal, you might face obstacles trying to achieve it. Productivity can falter as you enter a dog-eat-dog world. At your low points, it’s important to remember success is achievable and others have done it before.

It’s hard to become a self-made millionaire or billionaire, especially when so many try. So what is the secret of rich people? Does it come down to luck? 

Successful entrepreneurs can stay productive through their struggles. Here are the secrets five millionaires learned along the way.