Usually someone who is addicted doesn't know they are addicted until they started affected the next people around them, and again when they found themselves too much attached to what they are doing or and can't limits and take break from gambling then we should know they are addicted to gambling which is tantamount and equivocally of seeing the therapist for a solution and remedies.
It plays out that way for some individuals, that it would take the next person close to them to call them out on their shit before they realize just how deeply addicted they are. For others, they would understand it from the point of having anxiety over the game. When you just don’t play or haven’t play, you feel like you are missing something, like a win is about to pass you but when you just don’t win everyday. When you recognize this, then you would know their is an addiction problem looming.
It's common this way and of course whenever a gambler doesn't gamble for some minutes or days it becomes that obvious they are missing something very important, like they could have win a life changing opportunity while at idle moment. But still, even when they start gambling it becomes that common for them to still lose something very important while gambling and its not that easier to predict winning while gambling and one thing we should know is that gambling can never be predicted when someone would win game or not. In reality they feels they have all the opportunities to win, and one thing that makes gamblers gambles at every moment is that they felt gambling could give them what they needs at the moment without knowing that gambling doesn't work that way.