てこそはじめて (te-koso-hajimete): Only after; only by

Only after; only by

Vて + こそ（初めて）
Notation: N = noun; V dictionary = dictionary-form verb; V stem = the stem before ます; plain clause = plain-form clause; negative stem = the form before ない. Follow the attachment shown above.

Emphasizes a necessary condition for a result to become meaningful or possible.

自分で資料を確認してこそ初めて、難しさが分かる。

Only by checking the documents yourself do you truly understand the difficulty.

自分で先生に相談してこそ初めて、難しさが分かる。

Only by consulting the teacher yourself do you truly understand the difficulty.

自分で計画を見直してこそ初めて、難しさが分かる。

Only by reviewing the plan yourself do you truly understand the difficulty.

自分で会場を下見してこそ初めて、難しさが分かる。

Only by inspecting the venue beforehand yourself do you truly understand the difficulty.

自分で十分に練習してこそ初めて、難しさが分かる。

Only by practicing thoroughly yourself do you truly understand the difficulty.