Answer: 

Rigour is a steadfast mind. When we do something, all kinds of thoughts appear in our mind, but we let them pass and we stay in direct contact with the real thing.

Being rigorous is not clenching our teeth or being a fascist. On the contrary, it is to be utterly kind, attentive, generous. That’s the rigour of zen.

That steadfast mind is our consciousness flowing, stopping on nothing. When we look, we only look; we don’t judge, comment, or think about using it for our next novel or to show off in social circles.

We forsake that steadfast mind out of fear, out of greed, because we want to be admired, recognized… it always has to do with me or mine.

The authentic steadfast mind is not hard, but soft.