I don't condition, but I ran track and played football years before integrating the way of Parkour into my life, so maybe it's my natural athleticism that gives me the privilege of progressing rapidly in Parkour, without any additional training.
And to be more on topic, I don't think Daniel meant what he said literally, just figuratively.
You can fall anytime, but you are considerably more likely to fall when fear places a role at that specific moment.