Like Lisa said, the path through the stages of grief is not usually a straight line. Sometimes they overlap. sometimes a person may skip one. Often it can feel like you're finished with a stage only to find yourself back in it. As in your case, a trigger and bring up the fear again, and the sense of loss, pulling you back into a depression stage.

That is normal. Once I came to a point of acceptance, that didn't mean I no longer experienced moments of fear or looking back longingly at what I'd lost. As a matter of fact, the coming 5 year anniversary of Dday has me thinking more about it all than I've done in a long time. But now it isn't so much of a depression, but a distance sadness, offset by the gains we've made in our relationship.

One suggestion. If you've not read it, get a copy of "His Needs, Her Needs" by Harley. If you have read it, might be good to review it. Reason being one of the keys I think helps both of us to heal was learning to show love to each other, and rebuild that love bank balance the A tore down. Doing the hard things of rebuilding goes so much better when you feel you love her and her actions and words are instilling a surety in you that she loves you. It is like oil in the engine of rebuilding. Without it being there and fresh, rebuilding will tend to become a grind and not feel worth the effort. She also needs to read it. Best to read it together and discuss any insights into how you're relating to one another.

Note: I'm not saying you and her don't love one another, but that you both need to ensure the needs you are meeting in her and her in you are communicating to each other, "I love you" in such a way as to make deposits into each other's love banks. If that isn't happening on either end, it will make healing from this much more difficult.

It would also be good for her to read/review "How to Help Your Spouse Heal from Your Affair" by Linda McDonald to make sure she's doing all she needs to do to help you heal. Keep in mind, one year is rarely, if ever, the time when a relationship rocked by an affair can say "it's behind us now." Like in my case, and we healed faster than most, I don't think we really began to feel it was totally in the past until our forth year. By that I mean it is no longer this looming cloud over us. Each year became easier. But year two still was rough.

Now, some people do get to this stage, our fifth year, and don't feel it is over. They've not healed. They still don't trust their CS. The cloud is still there. Most often this is due to a CS not addressing the causes and weaknesses in themselves enough to ensure a no-repeat. The BS never gets to a point of feeling safe. The affair never feels "over." I think that is why you and many of us at times look for a "why." We want something tangible we can fix, that will solve the issue. But I'd suggest instead of focusing on the why, focus on the how. Not to cast blame, but to discover what boundaries were crossed, what mindset allowed it to be an option, what personal shortcomings and vulnerabilities in the CS that need to be addressed.

Then in addition, if you communicate your love to one another well, that gives the best chance for rebuilding success and for true healing. One of the things that convinced me of her love for me again was seeing her endure the painful soul-searching, guilt, and struggle to kill her love for the AP. She proved she wanted me and no one else. And now though I'm no longer so naive to think it could never happen again, I have no fear that it will. It is now a part of our history, but that is all it is now, strange as it may be to look back on that time period and wonder at how we came through that in such good shape.

So that's the broad picture to keep in mind. Year one is only the beginning.