Thirukkural 489

எய்தற் கரியது இயைந்தக்கால் அந்நிலையே செய்தற் கரிய செயல்.

Eythath kariyathu iyaintha kkal anthnilaye Seythath kariya seyal.

When difficult circumstances converge and align, that very moment becomes the forge for difficult deeds. Strike then, for the opportunity will not wait.