While trading we have to follow few rules and without following those rules there is no way to be a successful one except a successful by chance. There are lots of rules of them greedy plays a vital role. While trading never be greedy. If you become greedy while trading then you can be assured that there is 90% possibility to be a lessor.
You're absolutely right, we should sets limits on when to stop and end the trade. I remember getting to greedy during bitcoin ATH last december 20k I was hoping it will still go further but sadly it started plummeting still waited for it to rebound but then it continue falling.