You have every right to grieve over a 6 year relationship. That's a long time for one, especially nowadays. I recently got out of a 7 year on again/off again relationship myself. I'd be lying if I said it was easy. It comes in waves. I still get thoughts like "oh, he loves stuff like this... oh, wait...". While it feels like something we will never get over, over time we will notice that it hurts a little less every week. You definitely have an unlimited time to grieve. Allow yourself to feel it. Don't shove it away, yet don't let it overtake you. Keeping a routine for yourself, and adding parts to it to specifically pamper yourself, is something that personally helped me.