http://blogs.nature.com/boston/2012/09/27/guest-post-science-is-about-passion-find-yours
Having a passion for science. Knowing that what scientists are researching also help people is great. I don’t think anyone can last in the scientific field as a scientist without having a passion for it. Scientists may develop this passion in various ways. They may have a genuinely inquisitive or curious nature. Or they may have parents who instilled a love of learning in them. Or they could have had experiences in life that helped them develop this passion. They could have all three, two or one.