From where comes this myth of rationality?

We are not rational beings. None of us. We like to think that we are, we like to point to logic and reason as our cornerstones, but still, we are not rational. We are emotional, passionate, illogical beings, and the sooner we realise it the better.
The assumption that we are rational beings leads to all sorts of pain. It leads us to believe that if only we acted in just such a way, people would respond just as we want them to, and all would be well with the world. It makes us think that when things go wrong, there must be a reason: it must be something we did or something we said that made the person we love turn away from us. It makes us work over again and again past experiences and failure, worrying away at them, trying to figure out what we did wrong, what they did wrong, what went wrong.
But really, that's all bollocks. We are not rational beings. We do not behave in a rational manner. Our decisions do not submit to dissection by logic. Half the time, we do not even understand why we do what we do. Certainly we rarely understand why other people do what they do, or how our actions have influenced them and how their actions influence us.
When I was about 20 I was introduced to Daoism, and I've claimed to be a (bad) Daoist ever since. But in my shade of Daoism – and every Daoist has their own shade of the colour, no two the same – logic and reason are rejected as insufficient. Instinct, gut feeling, honesty with one's self, the recognition and rejection of wishful thinking, the low way (the way of water), seeing through constructs, they are the only way of really making sense of the world, because logic cannot ever cut the mustard.
The last few months I've been trying to apply logic to a situation that could never submit to logical analysis and which, in its recent conclusion, proved that logic doesn't work. If you hadn't figured it out yet, crw and I are no longer an item. What began in public ends in public, I suppose. But no amount of trying to figure out what went wrong will ever work. I can't understand it. I doubt I will ever understand it. The best I can do is learn to accept it and move on. I need to go back to my Daoist roots and stop trying to think about this in the terms logic and reason and start just reacting emotionally, instinctively and with honesty.
And I suppose this is step one.