惟有

The ancient people who was successful, not only had exceptional talent but also had unflinching will.

古人立大事，不惟有超世之才，亦必有望忍不拔之志。

Only such a striver is valuable.

惟有这样的才是富有价值的。

But inapt as I am, will follow your advice and perform my duties to the best of my powers.

虽不才如，当谨如尊谕，力所能及惟有天职也。