When I interact with reality, I'm going to be interacting with the reality that is, not the reality that I think is there. Imagine a game of chess: if I'm deluded about where the pieces are, my moves are unlikely to produce a good outcome, because the other player has the advantage of knowing precisely where my pieces are. It would be the same in a martial arts fight. If you're going to land a blow, you need to be able to see what you're doing. This is why reason, and in particular humility about what I know, what I do not know, what I cannot know, my own perceptual, cognitive, and reasoning abilities, and my universal and particular propensities to see things wrongly, is so important: if I misapprehend what is going on, and furthermore fail to realise this is the case, I'm sunk.
The problem I'm facing is not just moral and spiritual: it's cognitive. Sure, the moral and spiritual comes first, and this goes a long way to sorting out the cognitive problem, but the cognitive side of things needs a little direct nudge as well.