Let your emotions rule you in trading and you get to lose it all, traders should never let it out, and the more you know how to tame yourself, the better for you. Trading is certainly risky but there are good approaches to it that will lighten all the dangers in it, and the number one rule is that you should never trade when you are not yourself. No matter how you believe you are experienced, you can only enjoy the experience when you are still yourself, but when emotion has set in, that means it is no more you that is trading but the mention in you. This is why it is good to take a break when one feels an iota of emotion. This starts when you are passing aggression, or overtrading, maybe because you are greedy or you want to recover back your losses.
I see your point, trading out of greediness can result to a failure, better to trade when you are well prepared and not just trying to add more with your winning streaks, there are many factors that will affect you, having that kind of confidence which most of the time reflects in making mistake, not saying that you won't succeed but if you are not well prepared and you are just aiming to earn more, it's a risky way of trading and can ends up losing your investment.
For the latter, the result has always been losses, no trader will be trading with the wrong psychology that will be able to make success unless the trader is lucky. Even for the luck part, you can only be lucky to make profits or recover back your losses at times but that will not take you anywhere near a successful trading career itself. Let us always be practical and disciplined as we trade, we should shun greed and fear, and we should shun the urge for overtrading or risking excessively. They can't help but make sure that they set our accounts to zero balance ($0).
Yes, aside from luck the outcome mostly against your position, you need to have a good planning and strategy to make things be more successful and lessen the chance of losing your capital, having that right knowledge is always your edge when dealing inside trading.