For me, I feel like it's probably easier to quit when you're losing because of the hype around the winning, it's really difficult to quit when that's what is happening not to mention that it's easy to see yourself quitting when you know and are aware that you're bleeding money, it's much more logical for you to quit as soon as possible, that's how simple I think is the reason why it's easier to quit when you're on the losing streak rather than on a winning streak and I think a lot of us here have the same sentiment and think the same obvious thing.
both actually require experience and good emotional control. Stop when you win, of course, to secure your win and be able to enjoy it. Stop when you lose to avoid bigger losses.
I personally tend to chase losses until my fund allocation runs out when I lose. It's easier to stop and get out of the game when you win because there is a desire to enjoy the victory for me.
Of course, every gambler has different thoughts and habits.