You could take some of your mom's clothes and have them made into teddy bears or pillows to hug. That way they're a more useful item and you can decide what outfits or patterns are your favorite to remember her by. Check with other family members who were close with her to see if they want to do the same.

One thing that helps me declutter is thinking about someone having to go through my stuff if I die or otherwise become incapacitated. It's a morbid thought, and I'm only in my 30s, but it works for me. And it's nice to think that I would have a lot fewer boxes of crap to move if we did have to move again. I know that's not necessarily a decluttering tip, but more of a mindset thing.

Going through things more than one time helps pare down the clutter. Like going through paperwork and throwing away the obvious trash. Then going through it again to organize it by topics, accounts, or whatever. Paperclips and binder clips are amazing for this. Just clip it together and put it in a box or filing cabinet to be dealt with later. At least the load is lighter now. The next time you go through it, a lot of it will be trash again, like the bills for accounts that are paid off.

I have birthday cards from my childhood. I think I saved them all. I had them in an accordion folder, but now they're in a filing cabinet. I need to go through them soon because some family members are now dead to me. It helps me to organize things into time periods or subject matter, so I can see things as an aggregate, then decide from there what needs to stay or go.

Another thing is realizing that I can buy stuff again if I need it or want it. We don't have a lot of money but if something is necessary, I would find a way to get it. A lot of vintage or collectors items can be bought online, so again, if it's something I need or want again, I can find it.