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.
So the question of whether it is easy to quit when winning or when lossing applies to individual differences. Someone who is greedy will find it difficult to quit while winning and that same greedy man will be willing to chase his losses until he losses all.
That could be a good approach in paper, but when you are there, it's really hard to say. I mean yeah, you already made a withdrawal of $400 and just playing that $100 and by chance you lose it, maybe you are going to think to deposit and try to get that $100.
I'm sure gamblers here at one time in their gambling activity has done it. Not about greedy I guess, but it's more on the mentally of not wanting to lose. So in that case, it's better to withdraw all of that $500.