Kural - 467

Think, and then dare the deed! Who cry,
'Deed dared, we'll think,' disgraced shall be

Explanation
Consider, and then undertake a matter; after having undertaken it, to say "We will consider," is folly.

Tamil Transliteration
Ennith Thunika Karumam Thunindhapin
Ennuvam Enpadhu Izhukku.