So my question is this,as a gambler what mistake have you made when gambling that prevented you from winning big.
Let's discuss.
Greedy is basic human nature, nothing is wrong with that. I ever in the past when didn't take advantage of the opportunity so that make it all gone. what we can be done this is how to manage it. The meaning is, we should not do the same thing again in the future. So when we have the same situation again, we should be as much as possible to control it. I know $1200 is big money, who doesn't want to get big winning, but if the reality is we only can have chance wins of $200, there is no harm if only take that $200 only.

How is there nothing wrong with greed? It's a negative emotion that makes you do things that are unnecessary only to get extra gains over what you are already getting or have gotten, and that usually makes you lose what you have already got which is why it is something that we should avoid at all costs. A greedy person can barely become successful at any venture, be it gambling, a business, or any financial situation in your life, be real and try to get what is rightfully yours or what you are getting out of luck but never get greedy.
The thing you mentioned at the end is exactly what greed is all about. When destiny is giving you the opportunity to get $200 which you can get immediately but you become greedy and wants to get $1,200 that only is a possibility and you might not even get it, you will even lose the $200 that you could get and might not get $1,200 as well.