Most people have no idea what it takes to do a PhD. People commonly think certain individuals have some kind of magic intelligence that allows them to memorize things and crank out facts and ideas like some kind of machine. My ex-aunt had such a mindset, and had an irksome habit of making comments such as, "Well you must be looking forward to starting school again. It's easy for you, because you're smart."
Yes, this woman is a bitch, and that's partly my point. Or rather, my point is that I never told her to her face that she's a bitch, because I have a lot of self control. Self control, along with self-motivation, are two of the most crucial qualities for someone attempting an advanced degree. These qualities allow you to endure the opinion of pompous tenured sexist bastards, to stay in your office and work while your friends are going on tropical vacations, and prevent you from strangling undergrads who suggest that you're not fit to be a graduate student because you can't answer their off-topic questions to their satisfaction (it's notoriously difficult to finish your thesis while in jail).
Another quality that will benefit graduate students is patience. The uses for this quality range from enduring speeches by blowhard members of the upper administration, to listening to blowhard members of your department spouting facts literally just because they enjoy the sound of their own voice. Besides the ability to endure a two-hour lab meeting culminating in zero final decisions on the matter at hand (the wording of a figure legend in an appendix of a paper that hasn't yet been accepted) a type of existential patience is also beneficial; the power to accept that some questions will never be answered, the ability to endure years of minimal pay without opportunity for advancement, and suffer a painfully low ratio of successful to failed experiments. (Tangent: I hate when people rationalize the low pay for graduate students.)
I think that some people might label me as argumentative, but in my mind I'm just refusing to be a doormat. I have a lot of patience, and self-control, motivation; I'm a hard worker and fairly intelligent and organized. None of those things align with me having to endure intentional OR unintentional insults, jibes, or uncalled-for/nonconstructive criticism without saying something. When you live your life acting as if you have a subservient personality, then you default to those behaviors and thoughts. Is it really a mystery why so many of our academic high fliers have such deviant personalities? At least part of that has to be a survival mechanism as a result of this kind of treatment.
To get a PhD, you have to have some smarts. You also need intense determination, maturity, self-esteem, and control to remain sane. I don't look down on people who leave our PhD program; most of them are probably doing what's best for themselves. In fact, sometimes I think they're wiser than the rest of us.