(2.3.2.5) Measure, dismiss, put together
Social ecologist Peter Drucker also says:
>In my observation, those who achieve results do not start from work. ... They do not start from the plan. They start by clarifying what takes time. Next, to manage the time, they abandon non-productive demands on time. Finally, put the time together. Therefore, the three-step process of logging, organizing, and combining time is the basis of time management for achieving results.
(Note: It is a translation of the quote from the Japanese version. It should better to quote from the original English version. "The Effective Executive" section 2, or "THE ESSENTIAL DRUCKER ON INDIVIDUALS" part 3 section 3)
You should not use the time because it's a job, should not use the time because it's a plan, should measure and clarify how you use the time. It is a common idea for the Pomodoro technique and the TaskChute.
This idea of "measurement first" is well-known to the programmer: when you want to speed up the program, you should profile (measure consumed time) in detail which code spend time.
If you know how much time you spend on what by measuring, next you decline the less productive task, which takes much time but makes less achievement. You get the time which you can decide the purpose.
After that, you combine the shredded time to the big chunked time. For example, you can check e-mails in a shorter amount of time. So you should not do it during a big chunk time. I describe the procrastination from an important task in (2.3.2.1-2) Metaphor of hiking.