The goal you set must be challenging. At the same time, it should be realistic and attainable, not impossible to reach. It should be challenging enough to make you stretch, but not so far that you break.
If there is a symbol of our age, perhaps it is something that every factory worker does each day of their working lives -- I refer to clocking in. (Very soon probably they won't even have to do that; the clock will itself observe them by radar.) In the ancient world when a person entered a temple, each made a votive offering to a god or a goddess at the door. As twentieth century people file into their shrines, they obediently pay their due to the god that regulates their lives -- the clock. It is the clock that measures us, that silent witness that keeps our going in and our coming out and relentlessly records our every movement. That is where all our organization and machinery to free us from time, to save us time, has brought us. Never before have we had such control over things, and never before have we been so enslaved by them. And of nothing is this more true than of time.