Maxim

A few causes drive most results (the 80/20 rule).

“Occupy thyself with few things, says the philosopher, if thou wouldst be tranquil.”

Effort and outcome are rarely in proportion. Find the vital few things that matter and give them your best attention.

Related expressions

“For many outcomes, roughly 80% of consequences come from 20% of causes.”
— Joseph M. Juran (after Vilfredo Pareto), Pareto principle, as summarised by Wikipedia (paraphrase, not a direct quote)
Management & engineeringModern (1800 – 1950)relation: expressesProbablesource
“We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%.”
— Donald Knuth, "Structured Programming with go to Statements", Computing Surveys 6:4 (December 1974), §1; wording checked against a scan of the paper (the paper prints "3 %")
Computer scienceContemporary (1950 – today)relation: similarVerifiedsource
“Martha, Martha, thou art careful and troubled about many things: But one thing is needful:”
— Jesus, Luke 10:41-42 (KJV) (kept as a related saying about focus; not used as independent attestation of the 80/20 rule)
ChristianityClassical (200 BCE – 600 CE)relation: partialVerifiedsourceTranslation: King James Version (public domain)

Moral Rank 38.8 · Evidence E = 8.68

E = ln(1+1.25) + √1.25 + 3·1.25 + 1.5·2 = 8.68