Work expands so as to fill the time available for its completion.
It's Monday morning, you have the full week ahead of you and plenty of time to accomplish everything. No need to make a detailed plan and set specific deadlines, right? The deadline for "everything" is simple, it will be Friday.
Then, it's Friday and you realize that you didn't get everything done...What happened?
Well..., not only were you probably encountering distractions, called "Life", most likely Parkinson's Law, which states "Work expands as to fill the time available for its completion", was in effect as well.
5 days to accomplish everything is enough, you think. While it probably was enough time,
without specific interim deadlines and time limits, we tend to spend more time than necessary.
In order to avoid this, set specific time frames to accomplish certain tasks. For example: Instead of saying "I will write an email to a client", say "I will write an email to a client and allocate 10 minutes for it". Without setting specific time limits for each task, many people fall into the trap of spending more time than necessary, thus not accomplishing everything they wanted.
That is exactly why we get more done the day before we go on vacation! With limited time available and plenty of things to accomplish, we will make sure that we get it done in time!
From now on, allocate a specific amount of time for every task you need to accomplish.