Suppose our bankroll is $100 and it has already grown to $500, would you quit or continue? Conversely, if with our bankroll, we are down to $10, would you still continue or save the remaining $10? I used specific amounts to make it easier to discuss this situation. I understand that we all gamble with different amounts based on our income, but consider this as an example. You can mention any amount you want based on your personal experience; it doesn't matter.
We know how the gambling spirit does not let people quit when they are winning. We quit when we become perpetual losers. And that will after several attempts to recover our losses. Gamblers quit not because we want to but because we may not have more money to gamble with. But if am lucky to have made that gain as you described I will take out my profit and continue with the initial capital. If I lose that, I will quit. I will not struggle with the casino to get more gain.
So far and by now, we should already know that one major problem most gamblers have is greed, greed sometimes do not allow some people to think straight, and as such, they end up making decisions that end up costing them their hard earned money.
Personally, I am learning to quit when ever I win, most especially if the win is a significant one, I've done this like three to four times and it did worked, and I was super happy at the end of the day.
Best way to secure wins is to pause immediately the winning arrives, withdraw the profit made from the winning, and then continue playing with the initial amount deposited.
When for the times I've tried this, I ended up losing all the initial deposit, but I was happy because I already withdrew profit, which actually was way higher than my initial deposit.