A downswing is a phase or period of time in which a player sustains extended losses due to bad luck.
Dealing with a Downswing
Downswings are natural occurrences that belong to a game of chance, just like their counterpart the upswing, where one makes extended gains. Any game with an element of chance has a certain amount of variance since the behavior of the cards is randomized for short periods of time and will deviate from the normal distribution. In the long term, however, the behavior will settle down even if a downswing can last for more than ten thousand hands. Secondary factors can also enter play, like tilt or the influence of frustration on play.
The ability and mental fortitude needed to deal with long streaks of bad luck are the signs of a good poker player. A solid bankroll management scheme is necessary so that a player still has enough money at the end of the streak to begin making profit again.
The most common mistake is that players go on tilt during downswing and increase their losses unneccessarily, exhausting their bankroll so that they can no longer recover when the bad luck lets up.