For every separation or sadness I firmly believe there needs to be mourning.
Otherwise-- you'll either
a) Never get over it
b) Become really bitter/angry.
I was browsing through tumblr (again heh), and I find the most respect for those who admit that they still love their ex. It's not an easy thing to admit because of the hurt+ego, but it is these people who will truly find joy and meaning in their day-to-day.
We search so much for happiness that we forget to layan the mourning.
So, take time to feel sad. It's just as important as being happy.