most professional gamblers have their own strategies they can avoid big loses and just risk a little, knowing how to quit even you are still at lost is part of a strategy because you know their still a lots of time to play back and try your luck no need to push and keep you in a losing streak and burned out everything that you have.
Yes professional gamblers always play gambling with strategy and planning. They never play gambling with blind eyes. In fact they have good experience in gambling, actually they play gambling for a long time and therefore they know all the tricks of gambling. And that is the reason that they mostly make money in gambling.