It's a very personal thing, obviously, but I didn't find the due date itself too bad - had a little weep in the morning and then just got on with my day. I did find the following couple of weeks tough going though, as I was mid-cycle on my due date, so I consoled myself that I might get pg that month - but didn't. It was also my birthday about 2 weeks after my EDD, which brought up the spectre of advancing age/decreasing fertility, as well as the notion that I'd expected to be a Mom by the time I hit 33... Not a good time, all in all, but I got through it and you will too. By the time I'd passed the point where he would have had to have been born, things got a little easier.
And yes, it is bloody unfair, and I hate that other people have to go through the same thing. 