Indeed, gambling must be used as entertainment or pleasure to fill spare time and limiting betting capital is the most important thing and can control yourself when playing.
play in a relaxed and calm manner when gambling for entertainment or pleasure and stop playing when you are in a winning position because it is the right choice and do not have the ambition to continue to win because it will result in losses and ultimately lose everything.
You said to play as an entertainment, I don't think anyone would be relaxed and calm at that time.
It is not bad to be happy when you win and be sad when you lost as long as you know what you are doing. Also, when we gamble, we already know that people will not always win so we know they already added the idea of them just having fun in the casino or a gambling site despite losing or winning, still it doesn't matter because what matters is we are having fun.