Pareto Principle

80% of the consequences are derived from 20% of the causes aka 20% of the effort creates 80% of the results

Also known as the 80/20 rule

It is an observation that life is not evenly distributed and should help one prioritise where the most meaningful impact on your work/life is, and therefore, where you should be spending your time.

This does, however, focus on current and recent opportunities and doesn't keep in mind where your future could lie if you pivoted from what you are spending your time on now - eg, leaving a corporate to start your business, or learning a new skill - which will always be ineffective in the short term, but could be v effective in the long term

“There is nothing so useless as doing efficiently that which should not be done at all.” Peter Drucker

As James Clear summarises very well, the argument is between being efficient and being effective. Deciding what to spend your time on is more important than making progress in the wrong areas.

Couple the 80/20 principle with Inversion (another mental model) - could it be that 80% of the issues in a given project or situation come from 20% of the customers/family members etc?

The downside of the 80/20 rule is that "a new path will never look like the most effective option in the beginning" - James Clear.

Following your passion should be priority before trying to be effective