Help: How to declutter when poor?

I'm downsizing from a 4-bedroom rental home to a 2-bedroom, and I need to massively prune my family's belongings. But every time I try to start decluttering, my anxiety spirals out of control because of the sunk-cost fallacy and "what if I need this? It's such a waste of money to buy another one later." Replacement costs these days are not insignificant enough for me to be comfortable purging some things.

I grew up low-income and even now, I'm comfortable but feeling the crunch with these rising prices, and there's no "fun money" in the budget. So yeah, scarcity mindset is totally a thing for me right now.

I also struggle with the idea of losing the memories triggered by gifts I've received, like a sweater my mom gave me that reminds me of Christmas, but I've never worn it. I've used objects as external memory-triggers to cope with adhd-related memory recall deficiency.

So, because of those two things, I'm super emotional/stressed, and normal "decluttering" advice online isn't helping.

Do you know any methods to overcome scarcity mindset and decluttering emotions?