Parkinson’s law
“Work is expanding to the same extent as time is available for its completion.”
Besides the Pareto principle, the so called Parkinson’s law provides assistance against your inner stressors. The law says that a task expands so as to fill the time available for its completion. A person that has to finish a task within the next 6 weeks is going to tinker around it for at least 6 weeks in most cases – although a similar result could have been realized within 1 week. This is not transferable to all single cases, but in principle the tip is set short time limits, which will enormously increase your productivity. At the same time you should lower your demands to make everything perfectly.
However, what you stand to gain is more than what you will lose, isn’t it?
Parkinson, C.N. (1957). Parkinson's law, and other studies in administration. Boston, Houghton Mifflin.