I am a sentimental declutterer (if that's not a complete contradiction in terms!). I can't bear mess and clutter but also attach a lot of emotion to things and hate throwing things away.
My top tips are:
1.Let yourself be sentimental - but limit it to just a small number of items. So, for example, I've kept the outfit each of my DC came home in from hospital as newborns, and a favourite outfit or two from each of their babyhoods, but not whole bagfuls of baby stuff. Same with toys/books etc. Keep a handful of favourites in a nice memory box, and sell or donate the rest.
2.Actually chuck away (as in put into landfill) as little as possible - it's too heartbreaking. Sell, donate or at the very least recycle components of as much as you possibly can.
3.Use the internet for selling - ebay, Vinted, Gumtree, Facebook Marketplace - whatever easiest. I have sold all sorts of items on Vinted, I get a genuine buzz from knowing that someone else is going to get use out of something I don't need any more. And it's amazing how the sales money builds up when you sell lots of bits and pieces for a few £ each.
-4.Be creative in donating stuff - think outside the box a bit. So not just the charity shop, but animal shelters, local schools, nurseries, youth groups, community or daycare centres. Budgets are so squeezed everywhere - you may well find that people are grateful and will get excellent use out of stuff you no longer need.
-5 Go slowly - no need to do a huge chunk at once. Pick one cupboard or box or bag of stuff and sort it. Little and often can really help.
As PP have said, there are those who are naturally happier to hold onto things and others who are happier getting rid. At the end of the day, you can't change who you fundamentally are. But there are ways to declutter and still be gentle on yourself.