Work expands to fill the time allotted for it
Growing up, I had come across Pareto law being quoted by several people on multiple occasions. Its only much later in life though I came across the Parkinson law.
Pareto principle, also known as the 80 / 20 rule, is the theory that 80 percent of the output is determined by 20 percent of the input. Extending it to work, it then means that its 20% of our efforts that determines 80% of the results. The key to being effective and productive is identifying these 20% activities.
Parkinson law postulates that work expands to the time that we allot for it. This is particularly true for work that is cognitive in nature. When we allocate shorter time buckets to work, we tend to find more efficient & productive methods to get things done. This is also the reason why shitty first drafts work.
The two laws used in combination can enhance your productivity manifold.