I think many of them known or have an idea on how much they're going to lose but they just turn their eyes blind when they're already losing.
Ego is hard to beat and recovering is much easier to think of than accepting the big losses that someone might have.
Those that can't track their losses or don't really track at all, many gamblers do that. They're having hard time in figuring out how much budget they will do to gamble.
I think that it's not an ego problem. They play with the hope of winning a jackpot and changing their life forever, they think they might be the luckiest one, so, loses doesn't matter when there is an endless hope.
Avoid drugs / drink as much as possible, they will make you loose some control innevitably.
I'm a little different, I drink a little alcohol and smoke while gambling. Maybe it's my habit, but the important thing is that I feel more comfortable gambling when using them.
You'll feel more comfortable because alcohol helps you to relax and makes you happier. The reason why it's recommended to avoid drugs and alcohols during gambling is that they lower your inhibitions and makes you do things that you wouldn't normally do, i.e. you take more risks during gambling.