Yes you said something right about the impact when we are unable to ignore the greed that arises in the mind, simply the point is greed will make someone lose something they should have gotten before, so never try to exceed everything when it has become your portion.
I understand that we never know about the right portion size, but by having a plan and being realistic I think you should have a plan about when is the best time for you to stop and secure profits.
Actually on the other hand it is okay to apply greed as long as we are able to accept the fact of regret, but in most cases the majority of them always find it difficult to really be open-minded, so it is better to be grateful for any amount of profit as a form of appreciation for the efforts we have made in analyzing the market.
Yea, anyone that choose to be greedy or take a harsh decision on their trade must be ready with the stomach to accommodate the outcome of their actions. Months ago, I created a thread regarding how I allowed myself to lose the previous profit I made from my trade and the cause of my lose was because I made a bad decision. After making some profits earlier, I should have stopped and repeat back the next day but I didn't stop and that was what resulted to me losing all the profit I made earlier.
Yes, the point is that we or a trader must always be aware of the risks, do not only think about the profit opportunities because it is clear that trading will always be a risky activity, especially when you fall into various impulsive actions due to being carried away by emotions or due to not being able to ignore greed for example.
When you treat trading in that way, I think it's the same as gambling, and as you experienced where you continued the session when you had already made a number of profits, I think one of the reasons is because your level of discipline decreased at that time which was caused by you being too focused on getting a larger amount of profit which encouraged you to make decisions at the wrong time.
Therefore, this is why a trading plan must really be owned and maintained by a trader, along with maintaining discipline in the sense that when you have reached your daily target, stop.