I though you might want to hear about my experience, but this is just what I found useful, and it may not be helpful for you. We all have different experiences and are in different places.
I found our first anniversary after discovery very difficult, too - I'm sure everyone must share that feeling. However, we had already decided to stay together and that we would work together to deal with his addiction (you may not be at that stage, or may be thinking of separating). I have to say that with him, there wasn't a 'just once' discovery - there were several minor discoveries and partial confessions on his part before the big one. So when we got to our anniversary, we had already been through a few cycles of discovery, confession and starting over. At first, I thought I wanted to ignore the anniversary, but realised that family and friends would be sending us cards etc, so it would be hard just to pretend it did not exist. Having decided to stay in the relationship, I decided I would put some time and effort into looking back over our time together and identifying all the good times we had enjoyed and the good things we still shared. I found it hard to do, but at the end of the process, I realised that we had a lot that was worth celebrating and a lot that was worth saving.
We kept the anniversary fairly low key (just the two of us at home with a nice meal and a bottle of wine), but used it as an additional opportunity to talk honestly about what had happened and how we would go forward. We both shed a lot of tears.
We've had a few bumps in the road since then, but my partner has kept moving forward and has continued to work to leave his addiction behind him. Anniversaries are different now - they used to be just a celebration, but now they are a chance to take stock of where we are, what we are doing well and what needs more work. Life after discovery is never the same as life before, so it is not surprising that celebrations now are different to how they were in the past (just different, not necessarily better or worse).
If I could give one piece of advice, it would be to accept that this anniversary and future anniversaries will be different. What they look like is down should be whatever feels right to you. If you want to ignore the day, or spend the day in bed, or go out and give yourself a treat just for you, or do something with you partner, then just do it. Just make sure you take care of yourself and get through the day in one piece.