Sometimes the person won't really notice it and thus result to depression and suicide, so it's better to have someone to check up on you, or while you are still capable, stop playing and if you really can't stop, then it's time to go see a therapist before it's too late.
Regarding what Salad Daging said, I don’t believe that chasing losses is what makes a gambler an addict, rather, it is addiction that makes a gambler chase losses.
When a gambler starts chasing losses and loses more and more, he falsely thinks that he has no other option but to keep playing in the hope that he will get lucky and make a huge win that may help recover his previous losses.