Try not to think of it as an anniversary of something cruddy. It's just another day. And just like every other day, we have the ability to chose our attitude for the day.
I think what I'm trying to say is that it ends when you allow it to end. I made it through the anniversary of my "bomb" without even realizing it. I didn't realize it because I was too busy living my life and enjoying spending time with SO. Now of course it crossed my mind a couple of days later, and I thought to myself, "Hmmm...I missed that. I'm surprised I missed that. Should I take some time to be sad about it now?" About 5 nano seconds later I said to myself, "What for? What would be the purpose of feeling sad about it now? That was in the past. Let it stay there. I have a choice about how to mark this 'anniversary', and that includes choosing NOT to mark it at all!"
I then went on with my day, happy and productive.
Perhaps this may sound naive? <shrug> I'm not sure. Whether it's naive or enlightened, it works for me! And what does Michelle teach us? Figure out what works, and do more of the same!