I do agree that you have to work hard throughout your academic life and at the beginning of your professional experience. But after you create a stable and solid base, you need to transform the working hard component into a working smart way of life.
I have met many employees who have been very dedicated to their careers. They are often the first people to show up at the office and the last ones to leave at night. They are very efficient, productive, and can also be "over-doers". Yet they never think out of the box and they take their jobs as it is on paper.
If you take a look at those who reach high career positions, they are the kind of people who seek to invest their time in an added value.
This added value often comes from communication and socializing. For instance, they tend to work on promoting themselves versus their peers, and hence increase their visibility in their professional milieu. This is what we like to call networking your way up. They are always on the look out for an opportunity and the next big thing, whether inside or outside their companies. And while these strategies may not be part of the declared job mission, they are your key to reach a higher status and to climb up the social and professional ladder.
So remember don't just focus on working hard. Your solid work will not do all the action, because you need to work smart too!