It's gambling, not trading or investing, so your confidence means nothing in gambling.
It's game of probability and luckiness, and whether you are very confident, it does not increase your probability to win with your bets.
With gambling, confidence is not important, the important factor is gambling responsibility. You must afford to lose your gambling capital, but even so you must gamble very responsibly to minimize your potential loss.
I think our confidence matters in every action we want to take although in most cases, it has little or no influence on the outcome result. Not only gambling, even in trading and investment your confidence doesn't have effect on the market and can not change anything. Your confidence in gambling or any other things can only give you a sense of responsibility devoid of doubt and blame. It's very necessary when it comes to gambling since it's a guessing work and you need to have confidence in your guess.
There's no sense in placing your money on games you don't have confidence in even thou having confidence doesn't mean you will win your bet. At least, it means you gamble with one mind when you bet on games with utmost confidence than gambling on games with uncertainty. Your level of confidence will actually determine how responsible to gamble.