Better than nothing hahha. A worse feeling when both frustration and regret are hunting you,but like what you said even you are in green it's still a good choice to call for the day to prevent losing everything as the tendency when you ain't able to stop and all the deposit are all gone, you'll be force to add more and suffer with the outcome.
Take your money either you earned some or lose some, then comeback when you feel that you can make something decent.
Gambling is a game of probability, so many players are like you, they prefer to take half of the winning offer or amount, instead of losing it all and gaining nothing, while some other gamblers too are willing to give in all their hope on gambling continuously trying to double up their money and few times they could be lucky and most times they will lose all their money.
Yes I agree with your opinion that gambling is a game of probability, a game of chance and possibility, there is no indication, certainty or even any guarantee regarding whether you will win or otherwise at the end of the game, meaning the best approach in gambling after winning is as you said, namely by cashing out half or part of the amount of the win, the purpose of which is so that at least we can enjoy the results of the victory we get rather than losing everything and leaving only regret.
On the other hand, that is also the reason why greed is always prohibited, it does not mean that you will definitely lose but to minimize emotions and regrets when the results are not as expected, one thing that gamblers must know is "there is no connection between previous results and subsequent results".