Not 80% complete

An important point about the Pareto Principle (80-20 rule) is that it is not about being 80% complete. The 20% you focus on, needs to get to 100% complete.

In fact that’s why you focus on the important 20%, so you can actually get something to “done” rather than having a lot of unfinished work which happens when you don’t concentrate your efforts.

It’s far more productive to finish something than to start it (starting is the easy part).