Did this recently for my Mam, although she's no longer with us so may be under slightly different circumstances.
First thing I did was I had someone to help. It's difficult doing it on your own and I found my sister and partner to be less sentimental than me. Sometimes I'd put something to one side and they'd ask why I wanted to keep it and it was like a sense check.
Another thing I found was that I would pass through a room more than once. First time it would be obvious what would stay and go, anything staying would be sorted and bagged or boxed. I was finding stuff my Mam had kept for 30+ years and seeing it was a bit of a shock to the system. Some stuff, once I went back through again, I didn't feel so strongly about keeping. It would have been very difficult to do one room completely then move on.
My dining room was full of boxes and my spare room full of bags of clothing once we had given up her flat and I sorted through it all again. Once more, with more time and seeing things again I was able to part with more things.
Books, CDs etc I went through with my siblings and we kept what we wanted, the rest went to the charity shop. She was into jewellery making and amassed quite a large collection of beads and little charms that she hadn't really kept organised. A family member was happy to take that and put it to use.
I think it helps giving things up to good use if you can find a charity you want to help. We took some rugs and Christmas decorations to a women's refuge charity and I felt better that they were going to a use my Mam would approve of.
Personal items, by going through them again I whittled down to two storage boxes to keep. Over time I think I'd be able to reduce further, the world wouldn't be a different place without things in a box I never look at, but I'm not ready to part with it yet.
Good luck OP, it is wearing but just chip away at it.