No, I do not keep all that stuff, there really is no need.
I have 3 x A4 size memory boxes, that's only because I'm now in my 60s and a bit too many years for one box. I have small things from my own childhood including photos and some school reports, bits and pieces form my marriage, a small selection of things to remember my babies, odd newspaper cuttings and sale details of houses I've lived in over the ages. You don't need all the art work your kids ever did, nor the stories they wrote. Keep a couple of the best in your memory box, get rid of the rest. Take photos if you must.
You do need to do some sorting out. Too many people spend their lives dragging round "stuff" that is never uses and not needed (and often never look at) thinking either that it's "sentimental" or that we "might need it one day".
Sort out all your clothes. You don't need anything you can't get into, nothing that's out of date. You need a couple of decent outfits for weddings/funerals, some work wear (if applicable), some cold weather outfits and summer hot weather outfits, a swim costume and underwear. Anything else can be sold, taken to charity shop or put in clothing recycling.
You do not need past babywear once your children are older....keep perhaps one special baby outfit if you must and a first pair of shoes if you have to. Get rid of the rest as above. Again, you can always take photographs of things if you must....lay out a collection of items on the bed and take a picture before disposing of them, not endless photos.
You do not need several hundred books, old CDs, defunct videos and out of date equipment. Nor do you need out of date packets of food in the kitchen cupboards, endless bits of kitchen equipment you don't use....
There is no need for mountains of paperwork, such as banks statements, when it can all be done online. I have a mini filing cabinet, it has 6 A4 drawers and is only about 18 inches high (sits on top of a desk). In it I keep the latest papers essential to keep, a drawer for finances (tax, credit card etc), a drawer for the car (receipts, insurance, MOT etc.) one for professional (exam certs, training certificates), medical, bank, the house... You only need the latest few bank statements, current copies of insurances etc.
A drawer for stationery is helpful, all your pens, staplers and hole punches kept in one place. You need one decent hole punch, not 5. Not even two.
To answer your question, yes, you really do need to clear all the stuff. Do you have friends who would help you? It can be emotionally difficult for some people, for others it's just that they haven't got round to having a clear out, or else they don't know where to start....