Get full transcription here
Get Decluttering Simplified here
There are a lot of different intensities to grief, so here is the definition real quick: a deep sorrow, or less intense; trouble or annoyance.
Ways you might not know you are grieving as you declutter:

Closing a chapter of your life (baby stages, relationships ending, career, old life, old body)
When moving, a deep loss of more than just stuff. The walls of your home, your community, comfort zone, familiarity, scenery.
Fear of losing memories, security, people.
A childhood wound trigger - financial history, home life, insecurity, memories.

Acknowledge your grief. The intensity can stop you in your tracks, but that doesn't stop the grief. The season of life is still over, the relationships, you are still moving. Acknowledge it, articulate it (with a friend or therapist, or FB group).
Then, find the things you are looking forward to next. This isn't fake it til you make it. This is sitting with the shit and then getting yourself out of it. Because the other choice is to just sit there indefinitely.