@Macha I've been through this. When you need to, take off to the bathroom or someplace private, have a few minutes of tears or whatever, then go back to work. Rinse, repeat. Then go home and have a good shower and a big cry. Rinse, repeat ad nauseum.
You can do this. For me, it helped to remember that the Victorians used to have a two or three year period where you were /expected/ to grieve intermittently, it's part of the wearing of black for that time period. We don't allow ourselves enough time to properly grieve in this day and age.
I'm sending virtual hugs.