Is it normal for grief (loss of a loved one) to hit you full-on years after your loss?

Five years later, my Mom’s death has hit me full-on. I’ve been battling depression for a few years and knew that crux of my sadness came from the loss of my Mom. I couldn’t allow myself to grieve.

Now, it’s here. It’s physically and emotionally draining, but, it is happening and according to my therapist, once I allow myself to grieve, my depression will be lifted and I’ll go on to live a happy life. Not dealing with her death has held me back.

Thoughts?