Quote from : Doctor Who: Borrowed Time Book

The thing about the Lexington International Bank ladder was that it was very long, and climbing it was very exhausting, and so Andrew Brown didn't have a lot of time to think about whether he really wanted to get to the top of it—and besides, since so many other people were climbing too, the view from the top must be worth it. So he kept going. He worked hard. He put his heart and mind and soul into it. There was an opening for a position half a rung higher than he already was. With a promotion, he might get two hours a week of a secretary's time. He'd go to more important meetings, with more senior people, and have the opportunity to impress them, and if he did he might be promoted again and then... well, of course eventually he'd be running the whole office. It's important to have a dream: otherwise you might notice where you really are.