I believe the best is to stop when you experiencing a streak whether good or bad. The reason is because if you start noticing you haven't lost a game and have been on a run you would want to taking daring bets without even knowing. And if you losing and don't stop it would get so serious that you won't even care what it would cost you to get a win. And most times, everything.
Yep setting a limit to your gambling activities is somewhat the best form to gamble, most of the times, gamblers get carried away with their winning stride to the point that they forget to apply limits to their Gambling, but as far as that is, we should not take winning strids to mean a luck that we can't avoid because in the end, we may lose everything if we don't walk away.
Having a winning streaks might be seen as a luck but this might be different all together. You can be winning and winning but that might be a trap for you to gamble with all your money thinking that you could win bigger amounts or you can make more money without knowing that you will become a loser by the time you can no longer control your gambling patterns making your to bet often to the extend of not getting any tangible results from your bets. There are so many things that can make gamnlers to lose money to gambling.