Restlessness or irritability when trying to reduce or stop gambling.
After losing gambling money, often comes back another day to get revenge ("chase" someone's loss).
Forcing into debt and even committing crimes just to have playing capital, and relying on others to provide money to alleviate the desperate financial situation caused by gambling.
Unfortunately a lot of these points tie together and the overriding driver would be lack of control. When people do not feel like they have control of the situation then they are more likely to "go with the flow" and potentially string together multiple bad decisions. If someone starts off gambling, losing a stack of savings they might have had, it drives them into large feelings of guilt, which heavily affects their decision making and depending on the severity of the loss they might have lost a rational thought process. This could lead them on to even worse things like stealing from friends, family or a company that they work in. Basically even if you do start from a comfortable position it is incredibly easy to lose a grip and you need to understand how the odds are stacked against you to restrain your losses.