You won't even think about trading under pressure if you are learning to trade the right way. You cannot trade under pressure if you read trading books, have mentors, be a part of peer group of traders. The people who are likely to trade under pressure are those who are greedy and want to make it a get rich schemes. Trading for them is short term and not a long term endeavor.
I use to wonder why people always put themselves under pressure of any sort just because they want to get rich faster, moreover everything is a gradual process and so it needs time to pass through every stages but just like you said, greed has taken over them, it's just like gambling that many others want to get quick money from all because of selfish gains other than gambling with what they can afford to lose. And mostly they fail to understand what works for the next person may not actually work for them in most cases.
Most people who go into trading under pressure never had the opportunity to pass through mentorship because they can't pass through series of time only to rush into trading when they know they can't get anything good trading under pressure, aside the greed you clearly mentioned I think most of the traders who fall under this category are basically those who sees trading as a thing of luck just like gambling they hardly believe that knowledge has a good role in trading for anyone who wants to be successful not just in trading but most of the things that involves investing money. I don't know if there are people who started trading and making profit without following the learning process I think those who actually claim to be making money every now and then on the Internet could be the major motivators of those who trade under pressure because of the things they upload without proof.
You onto necessary need to have a mentor in trading but if one is able to get one then good, I think trading is more about willingness to learn. People find trading difficult not because they no mentor but it is because they find it very difficult to learn.
Going into trading without having knowledge is very risky, not having knowledge about trading their are bigger chances to lose all your money in trading. Trading without knowledge if time is not taking you may not even have anything as luck because you don't even know what you are doing, which I think trading is even more risky than gambling for those who don't have any knowledge of trading.
Making profit in trading is very possible to achieve with learning but some people feels it is what they can go into with but their are more o know about trading and it can be achieved by learning.