Have you kept, for example, your old school exercise books? No. I have one memory book from the last day of sixth form and a signed shirt.
Text books from uni? For a time, then got rid.
Story books from your childhood? No, but DH's mum kept two toys she passed down to our child.
Your kids' clothes? Yes but only because we plan to have a second.
Artwork / handicrafts made by kids? Yes, but she's only 1. I would find it hard to let go tbh. Will have to have a one in one out policy and photograph the ones that get thrown away.
Your DCs old school exercise books? Too young. but I know DH's mum kept some key bits after she did a huge sort out when her sons left home.
Christmas and birthday cards? Some. Christmas cards I keep for a time as I like to recycle them as gift tags. I do find some of these hard to get rid of, particularly from elderly relatives.
Sentimental stuff e.g. cinema tickets, letters from friends, handmade gifts etc.? Ummm no I don't keep too much. And I regularly get rid. Eg) Lots of gig playlists and photos from my 20s I kept for years, I threw away. I think as one season of my life ends and things aren't so important to me or my identity anymore, it's easier to get rid.
Jewellery you don't wear anymore? Nope
Clothes that you're too fat for? eBay em
Old bank statements? Letters from HMRC etc.? Not bank statements cus you can get them online or order if you need them. And I've never needed them in my life. Other things like HMRC letters I keep for a bit. If I have to action it or it has details in I'll keep it. But if it's a reminder or whatever, i bin it. Now it's all by email and I delete them unless it's important.
Things "just in case" (e.g. 5 hole punchers)? Loads of books? Books, no. I tend to get rid every few years. I'd keep one hole puncher, two max. Never 5.