The two principles that when combined can 10x your productivity are Pareto Principle and Parkinsons Law. I first encountered these two concepts when I read the book 4 hour work week by Tim Ferris.
Pareto principle suggests that the 20% of input is responsible to 80% of output while 80% of input is responsible to 20% of output. With that, it is more productive to focus and deliver first the 20%(vital few).
Parkinson’s law suggests that the amount of work expands relative to the time allocated to it. For example, if you plan to clean your room in 10 hours you can finish it in 10 hours while when you just allocate 1 hour, then you can also do it.
Combining Pareto principle and Parkinson’s Law means you allocate minimal time on vital few activities. It is all about putting constraints in a smart way. We can see that through constraints we humans tend to be more disciplined and productive.