I agree that sometimes even if someone has choose to gamble with money they can afford to lose, it's still possible for them to become emotionally attached to the outcome of the game, the disappointment is inevitable when the outcome takes a negative turn and the money is lost. So it's not just about gambling with money one can afford to loose but also gambling with the right mindset and attitude.
It's normal for every human to have some form of emotional attachment to them loosing or not winning a game, so it's not a big deal if they get emotional at some point regardless of the amount that has been staked on the game but then what will really matter would be the reaction of such person after getting emotional for the losses, do they allow it get to them such that they now have to do some unhealthy practice and also somethings that will result to more losses.
Our reaction some times matters a lot a d that's why it's good to be disciplined and have self control, some persons have got this issues where they will loose a huge amount of funds and ywt they will be able to still cope and not behaving as if they lost a life and would want to perish along side with the person they must have lost, it's very important that we exercise some kind of restrain when we have situations as such so that we don't eventually get to suffer from the after consequences of such situations, we can try to see how to control ourselves regardless of the amount we lost be it small or big because our reactions there after has got a lot to do with the effects this will get on us in the nearest future.