I'm sorry. The healing and all the work you've done thus far is not a waste of time. This is just a set back.
Triggers can come out of the blue and anniversaries can be very hard. Hell, a certain way the wind blows through the trees or a particular food or song could serve as a trigger for me sometimes. It doesn't mean you're back to square one. No matter how bad the set back gets, you will never be in that dark place that you were two years ago.
I think it's impossible for us to move through life without ever having another set back or crying jag. It's a trauma and one that will, in some way or another, always be there.
Regardless, the main thing to remember is that it does not matter how many times you fall. We've all stumbled and tumbled down those hills on this shitty journey. What's important is that you get back up. Go as slow as you need, but the goal is to stand back up.
Two years is not that long of a time and your D hasn't even been final for a year. Give yourself a break. You'll get there.