〜ばこそ

愛(あい)すればこそ、厳(きび)しくするのです。

Aisureba koso, kibishiku suru no desu.

It is precisely because I care that I am strict.

ばこそ insists that is the very reason and no other

健康(けんこう)であればこそ、働(はたら)けます。

Kenkō de areba koso, hatarakemasu.

It is only because I am well that I can work.

のだ often follows, tightening the assertion

演説(えんぜつ)や序文(じょぶん)に現(あらわ)れる調子(ちょうし)です。

Enzetsu ya jobun ni arawareru chōshi desu.

It is the register of a speech or a preface.

Day to day it is 〜からこそ, or simply だから