I'm going through this ordeal right now with my toddler

My parents had such trouble with this when I was a child... I felt serious anxiety at the thought of throwing something away, and wanted to keep everything. My tip would be to clean out other areas in the house while your child watches (throwing away things you don't need in the kitchen, organizing DVDs etc.), hopefully it'll inspire them to do the same.

Idk about with toddlers but as someone who has had anxiety their entire life sometimes tossing something is really stressful. If they're old enough or can communicate their feelings well enough ask them? I haven't dealt with toddlers much.