negotiations are complex but, at their core, they are exactly the same as any other negotiation in life. It is in the interests of both players – in this case the UK and the EU – to strike a deal. At the same time, each player has a different view on exactly which deal to strike."
"So, what does this mean for the UK’s negotiating team, led by David Davis, and its ability to convince their EU counterparts? To have material impact now, the UK must be seen to commit sufficient resources to a no-deal scenario
such that the likely payoffs to the UK could imaginably be greater than payoffs from any deal the EU is currently considering. If the UK does this, a rational response from the EU would be to offer a deal that matches the payoffs to the UK in a no-deal world. A deal might then be struck."
The UK would indeed do well to prepare for the worst post March 2019. I would say the EU's main goal is to make Brexit as costly as possible for the UK, as a deterrent to other would-be leavers. If there is one thing to be learned from the way the Greek crisis was/is being handled, it is that, in situations like this, the EU does not do rational maximization of mutually beneficial payoffs. What it does do is try to make an example of those seen to undermine the union by not playing by the rules.