My biggest mistake is always over estimating my odds and probabilities, for exemple after losing 5 times in a row i get certain that i'm going to win the next time and i make a big bet and i finish losing again and that made my bankrolls vanish.
The same happens with me each time. Each time i go for gambling i loss and it gives me more confidence to bet again which eventually gives a huge loss again for me. That is the main reason behind why i always keep on staying far from gambling. Gambling has gives me profit but 100x to that i have losses with me.