Let us take poker or sports betting, for example. If there are winners, there must be losers as well. If there are millions in winning prizes, there must also be millions in losses. Those who are losing big time may still come back the following day and bet big amounts of money. Where do you think this money come from? Only from their previous winning? No, I doubt it. In gambling, it is not always a sunny day. These people must have other sources of income which give them a continuous flow of money.
In every sport, you have winners and losers, winning and losing are parts of every game. A poker player can win more than $100k in one tournament with $500 buy-in. There are many tournaments, micro or high stake tournaments, with awesome prizes. A poker player can gamble with money he previously earned if he is good. There are players like Daniel Negreanu and Chris Moorman who constantly show great winning results in poker, they constantly win big tournaments, but this does not apply to all players.
I said I know people who live from poker and betting on sports, like everyone else they also have losing streaks. Because of that, you need to know how to manage your bankroll! You need to know how to move profit on aside and continue with your strategy.