This is usually the first rule in most BJJ schools.
"Check your ego at the door". Sometimes the meaning is not so obvious.
In another forum, the topic came up about a male student informing a senior female student that he could "beat her up" in spite of her training. This caused the female to doubt her abilities and do some soul searching in regards to what she has done for the past five years (in regards to training). Lacking confidence in what you are doing is a major factor in students quitting. Sometimes they arrive at that point on their own........and sometimes they have "help".
Although this is not directly related to BJJ/MMA, I think that it's practioners might have a unique perspective on the issue.
What do you think?