On the knowledge of one's limitations

[radegund]

Cú Chulainn, near death, places his hand on his heart and says, "I give my word and I swear by the gods of the air, that I did not know until today that it was not a heart of stone or bone or iron that was within me, and if I had known that it was a heart of blood or flesh that was in me, I would not have done half of the valour of the deeds that I did."

Sometimes I know how he feels.

(The passage is from Aided Con Culainn, quoted and translated by Liam Mac Mathúna in the paper I'm proof-reading this morning.)