Work expands to fill the time available
It is a good habit limiting the time you have to work, since work usually expands to fill the time available. For example, if you have a day to do some work, you will take the day to complete it. But, if you have a week to do the same work, a day certainly will not be enough to complete it, probably it will take the whole week to be completed. Similarly, if you have a month to do the same work, it will take the month to be completed and so on.