the weakest link, the limiting factor, a bottleneck...

the weakest link,  the limiting factor,  a bottleneck...

明智周【從列寧的鏈圈帝國主義論看養身】
列寧曾經說過，一條鐵鍊的強度，並不是看它有多粗壯、打造得多精密，而是要去觀察它『最薄弱的環節』有多脆弱。
我們的身體也是一樣：個別部分的強大，並不會帶給我們太多好處；個別部分的缺陷，卻往往一瞬間要了我們的老命。
同樣的道理，會養身的人，或者說是老化速度比別人慢的人，往往不是因為他『做了什麼事』，而是因為他『做對了某一件事』，從而能夠有效、及時地補強身體上的『最薄弱環節』。

類似這種想法的用語是"Bottleneck - Wikipedia"

https://en.wikipedia.org/wiki/Bottleneck

Bottleneck literally refers to the top narrow part of a bottle. In engineering, it refers to a phenomenon where the performance or capacity of an entire system is limited by a single or small number of components or resources.

de Bono 的著作 Word Power 有此字眼的詳解。

顧問師將它發展成所謂的"限制理論"TOC：

The Theory of Constraints is a methodology for identifying the most important limiting factor (i.e. constraint) that stands in the way of achieving a goal and then systematically improving that constraint until it is no longer the limiting factor. In manufacturing, the constraint is often referred to as a bottleneck.

簡單地說，研究系統或其限制時，要注意最弱環節 (the weakest link,  the limiting factor,  a bottleneck)。然而，有時系統內部互動複雜，環環相扣，要了解最大/最小的"貢獻因素"很不容易。所以依照隨便找出的"最弱環節"來處理，可能只是局部的最佳化。

the weak/weakest linkthe person or thing in a situation that is less strong, skilful etc than the others Goalkeeper Gouter proved to be the weakest link.

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http://www.phrases.org.uk/meanings/the-weakest-link.html

A chain is only as strong as its weakest link

Meaning

The proverb has a literal meaning, although the 'weakest link' referred to is figurative and usually applies to a person or technical feature rather than the link of an actual chain.

Origin

We are most likely these days to come across the phrase 'the weakest link' in reference to the popular TV quiz show of that name, which originated in the UK, hosted by Anne Robinson, and was later syndicated for use in many other countries. The show, which relies on the demonstration of the abysmal lack of general knowledge by many of the participating contestants, is an example of the many 'humiliation television' shows of the early 21st century and is a sad spectacle.

It is clearly a literal fact that a chain is only as strong as its weakest link. The conversion of that notion into a figurative phrase was established in the language by the 18th century. Thomas Reid's Essays on the Intellectual Powers of Man, 1786, included this line:

"In every chain of reasoning, the evidence of the last conclusion can be no greater than that of the weakest link of the chain, whatever may be the strength of the rest."