Kural - 490

As heron stands with folded wing, so wait in waiting hour;
As heron snaps its prey, when fortune smiles, put forth your power

Explanation
At the time when one should use self-control, let him restrain himself like a heron; and, let him like it, strike, when there is a favourable opportunity.

Tamil Transliteration
Kokkokka Koompum Paruvaththu Matradhan
Kuththokka Seerththa Itaththu.