てこそ details
write + (and…) + only by doing X
kaite koso
only by doing X; it's precisely by doing X that Y follows
meaning: only by writing
頑張ってこそ、結果が出るんだ。
ganbatte koso, kekka ga deru n da.
Real results come only by trying hard. casual
挑戦してこそ、新しい道が開ける。
chousen shite koso, atarashii michi ga hirakeru.
It's only by taking on challenges that new paths open up. neutral
Examples
only by doing X — the result named afterward becomes true only because the action was carried out, and would not follow otherwise
頑張ってこそ、結果が出るんだ。
ganbattekoso, kekka ga deru n da.
Real results come only by trying hard. casual
挑戦してこそ、新しい道が開ける。
chousen shite koso, atarashii michi ga hirakeru.
It's only by taking on challenges that new paths open up. neutral
困難を乗り越えてこそ、真の成長が得られるのです。
konnan o norikoete koso, shin no seichou ga erareru no desu.
It is only by overcoming hardship that one attains true growth. formal
Formation
{V-te}こそattaches to て-form
Related patterns
Similar
からこそ singles out a REASON as the one true cause — from this reason, and no other, Y follows; てこそ singles out an ACTION or process as the one necessary precondition for Y. A cause explains; a precondition enables — swapped, a reason reads as a method.
Lookalikes
Both tack straight onto the て-form, but argue opposite directions — ても concedes the action changes nothing (降っても行く), while てこそ insists the result depends entirely on doing exactly that (努力してこそ結果が出る); one particle apart, opposite logic.