I personally think that there are many gamblers who know quite well that gambling is a game of numbers, but yet, refuse to learn math .
Such gamblers will be happy when they win big amount of money, but absolutely forget that they spent much more before winning that amount.
Personally, the feeling of excitement whenever you win somehow offsets the overall realization that my losses are still bigger than my profit! But in all reality, this kind of practice should be frowned upon given on how it can be potentially deceiving on the person. I hope that there is like a "profit/losses counter" that someone can create in order for the person to be aware of his general situation on his activities.
Slots is one of those games that I truly want to avoid. There is just no sense in playing slots due to the sheer luck that you have to experience in order to win. Sure, from time-to-time you may win small amounts of money, but I strongly believe that the system created it that way in order for you to continue playing slots.
I noticed this kind of behaviour from the grandmother of my girlfriend. She was playing slots and she initially betted $20 in the game with around $0.3 per spin. It got to a point where she almost lost all of her money but suddenly she won a "semi-jackpot" that jumped her bet from $20 to $50. Though that may be the case, she still lost all of her money since she continued betting.