I would concentrate on the task at hand but I would also concentrate on the quality of the time spent on that activity. It is all too easy to tell someone to regulate the time needed to do something, if they are going do it haphazardly or unwillingly. Which brings up another point I have against promoters of the self-management wave: advocating it's importance, does not always address the need of self-awareness. Is the person doing the activity because he wants to be fulfilled or is the activity being done because it is just imposed? Hopefully the person wants to complete a task because he is self-motivated and is not just driven by external factors.
Fulfilling a task does not necessarily entail its completion. So many of us get part of what we have do completed; one might feel just as fulfilled by going part of the way. This is especially true of the technological world we live in where with convergent technology pushing us forward many of us have not been able to deal with multimedia systems when we used to handle one at a time. So completing a task by getting hosted on someone else's website is a way of getting your own website done. Another point in favour of the incompletion is that we often do not have the physical time needed to do all the tasks needed to complete a project. This most often occurs in the film making process where executive producers, in big budget films would not necessarily want any of their staff to handle more responsibility than needed to get a specific job done. Hence lighting technicians are there for lighting and the gaffer is there to help carry the equipment so that the lighting person can concentrate on the illuminating the plateau.
Time is a critical measuring tool of how well you have self-managed a situation especially when time is money. Hence again in the movie industry if the film schedule goes overboard then the producer will have to fork out additional money to keep a location or to satisfy the actors and technicians on the set. Anybody who has been on film sets knows how an air of desperation because of working late can often obscure the quality of one's goal. So quality is a needed consideration too in proper management.
Some may like to associate self-management with meditation exercises geared to relaxing the body and stimulate the mind's ability to concentrate. But I have been able to relax and concentrate without these exercises, which I feel, are extraneous. If one sets a goal in mind and concentrates enough on achieving it, that person is bound to establish a means to obtain it. That of course means that the person has to resist being distracted or swayed from alternate choices. Repetitive tasks are best done when brain activity levels are low like when starting up early in the morning or before retiring to sleep. The time-management involves setting goals and priorities of what needs to be done first, what tasks show follow and when as well as knowing how long an individual task should take. If as in the book writing industry you normally get your material together before writing a non-fiction book in a month then perhaps you might reconsider completing that book if you haven't had the time to get all the information together or the publisher has given you a limit.