It's not really mood swings which is different from stress or depression that we are talking and this is what I am trying to say cause now we have exposure to lot of information that clogs up our mind and it's only a medical practitioner can figure out not from Google results.
Experiencing disappointment after losing is very normal but how long we carry that it's in our hands, we can sleep it through then it's okay but if we let that thing keep growing up then overtime it will lead to lot of complications and one of them is depression.
The gambling loss always create the mood swing by thinking about the loss money,because the money loss in the game will be the real money earned by the gambler.The meditation should be followed in order to get away from the stress caused because of the gambling loss.