Indeed, they think that it will be the same outcome as how they predicted it and once they start to experience that losing streak, that momentum will be pushed into frustrations and aggressiveness where emotions will lead you to lose everything.
The moment you start experiencing aggressiveness and frustration, the best thing to do is to stop gambling because if you continue gambling you'll end up making decisions that you'll regret later. As a gambler you should be able to control your emotions or they'll control you.
Some common mistakes that can prevent us from winning is greediness and lack of discipline. The problem isn't that gamblers don't plan their bets but the moment they encounter any difficulties they loose their discipline and allow their emotions to take control of their decisions.
As a gambler if you're greedy, you'll end up losing more money than you'll win because greediness makes you less satisfied about your wins and want to continue playing with anticipation of winning more bets but that doesn't play out as you planned so avoid greediness as a gambler.