Kural - 1153

To trust henceforth is hard, if ever he depart,
E'en he, who knows his promise and my breaking heart

Explanation
As even the lover who understands (everything) may at times depart, confidence is hardly possible.

Tamil Transliteration
Aridharo Thetram Arivutaiyaar Kannum
Pirivo Ritaththunmai Yaan.