网友应该知道这个句子：
He who doesn't reach the Great Wall is not a true man. 不到长城非好汉。

1. 这里，He 不是指特定的他，而是泛指任何人，后面可以直接跟定语从句。那么，我们就完全可以说：
 He who permits his thoughts to control his actions is weak; he who forces his actions to control his thoughts is strong.
——就像上句格言一样，句子没错，但主语太长了，是不是感到头重脚轻？

2. 为了句子匀称，避免头重脚轻，我们换一种说法，把定语从句后移：
He is weak who permits his thoughts to control his actions; he is strong who forces his actions to control his thoughts.

3. 上句的定语从句与先行词被 “系表分隔”，仍然不够理想，干脆“主系表”完全倒装，让定语从句紧挨着先行词：
Weak is he who permits his thoughts to control his actions; strong is he who forces his actions to control his thoughts.

——这就是网友句子的来历。希望全面了解和掌握这三个句子，学会更多的表达方式。

【特别说明】主系表结构不是随便可以倒装的。 例如 “他很高兴”。我们通常说：He is happy. 不说：Happy is he.
只有在句子结构需要变化的情况下，才不得已而为之。