'Work at your job and make a living,
Work on yourself and make a fortune.'
Having a job earns you a living. There's nothing wrong with having a job, especially if it's something you love and you earn a good living. However for most of us, you can survive on your pay, but it's difficult to get ahead in life working for someone else, without extra skills.
If you have a job and work hard at it, you'll make progress, but there's a limit to how far you get without working on yourself. If you work on yourself whether you are employed or whether you have your own business, then your life and likelihood of success will improve greatly.
This is because working on yourself means that you improve yourself, enabling you to learn more skills, improve your way of thinking and improving all aspects of your life. This way you add value to yourself as a person and thus add value in your job or business. You would then provide a better service / do a better job, giving added value to your company and clients.
Mostly, adding value by working on yourself will have the greatest benefit to you, by improving your mind, body and soul and living the life of your dreams.