You can have an external deadline or an internal one. The external deadline is set by someone else. The advantage is that you have to meet it, more or less. It is beyond your control, so you can tell yourself that you are forced to get your work done by a certain date, the deadline. The disadvantage is that you thus allow someone else to set the schedule of your writing.
An internal deadline is one you set for yourself: "By the end of the year, I will finish the book." The problem here that, since the deadline is under your own control, you can cheat on it without repercussions. "So what if I don't make it, only I will know it." The advantage, though, is that it is under your own control. You can even move it up if you want. If your own internal deadlines come sooner than the external ones, then you will never have to worry about external pressures.
With goals not related to time, the principle is the same. You can have tenure as your goal, which is an external one, or choose an internal one unrelated to tenure. Having tenure as your goal is like saying that you don't want to get cut from the team, that you want to go on. If you express your goal as being a nationally known scholar in your field, you will still get tenure (if you were going to anyway) but you are setting the goalposts in a different way. It's easy to get depressed right after tenure, because achieving a goal like that is unsatisfying. It means you didn't get fired, that you are still on the team, but little else.