To use gambling as a means to earn a living.
Not everybody can do this, but a minority can. These are the professional gamblers. Professional gamblers literally gamble for a living. How is that possible, you say? How can you make money from a gamble? Well, what these gamblers do is they cut the gaming part out of the games they play as much as possible. Games of skill which bring positive results - video poker, poker, blackjack, craps - are what the pros like to play. When you gamble in this way, you are not really gambling like ordinary folks do. You're playing for money. Actually, it's a very cool job if you ask them!