Thirukkural 848

ஏவவும் செய்கலான் தான்தேறான் அவ்வுயிர் போஒம் அளவுமோர் நோய்.

Eva vayum seikalan than theran av vuyir Po om alavu mor noy.

One who acts without knowing his own limits and capacities acts foolishly. For that life, uncertainty itself becomes a disease.