what does it take to do a Phd?

I always wonder how ppl do research and end up getting doctorates. Assuming tht every Phd student publishes papers worth talking, wht exactly in them drives to be a ever learning student. I feel is tht they possess that extra bit of curiosity abt the things the way they r working and more importantly the incessant perseverance to keep on trying till they get the results.
I really admire tht quality of a Phd student---to persevere. Wish i too had tht in excesss....