No gambler treated gambling as entertainment all the time he is playing, there will always be a time of changing or shifting your mindset, we are tempted to be like that, we are just humans and tempted to be greedy especially when money is involved.
It's mean your self control skill is bad and you need to think what's the reason your mindset is changed. I was a gambler who gamble for money, but mostly I didn't achieve my goal and I'm not happy with the result. After that I learn to change my mindset to gamble only for entertain, regardless of the outcome is, I always happy since gambling is fun. Until now my mindset is never changed and gamble is always to entertain for me.
It is true that greed is already part of is that is why it always take extraordinary move for us to overcome the greed in us. Everyone has it in us and it only need to be established for it to start creating difficulties and problem for us when we do things or react to something. Gambling is meant to be fun filled but at the same time, we all want to make money and pay our bill and that is one of the major reason why we do see even the rich and poor going into gambling. Everyone want to make more money and gambling had been a quick way for us to double our Capital if we know what we are doing as a gambler.