Your stuff shouldn't be the equivalent of your memories. Yes, looking at a special tree ornament or a photo does spark memories that perhaps you haven't thought of for some time; and while you may not be quite at the level Brian and I are at (getting rid of almost all of our papers), you are certain to agree with us that hotel toiletries, old Christmas and Birthday cards, and childhood participation ribbons do not hold any particularly special memories anymore.
Think about a time in your life when you did lose your memories i.e. you lost your mind. Like when you computer crashed in college - buh bye to 5,457 photos of you and your friends - taking selfies before they were called selfies. Or how about when your phone was stolen - some contact numbers were never again retrieved. What about your car being broken in to: see ya later CDs, spare change and maybe even your wallet (along with your ID and more importantly your rewards member club cards). I'm sure most of us have experienced one of these three scenarios in some form. And when that happened you had to just get over it. Your 'memories' in the form of stuff were ripped from your forgetful or unlucky paws. Aw shucks.
Now think about how different it would have been if you could have just shrugged your shoulders and announced to the karmically cruel world: "meh. It was only some stuff, I've still got my memories." Because seriously, stuff can be replaced - your mind is here to stay (ignore extraneous circumstances like early onset dementia and Mad Cow disease).
So try it - let go of your stuff and hold on to your memories. This means not equivocating a cookie cutter to your grandma's cookies. You've got that correlation safely stored away in your brain - think it, say it, reminisce about it; but don't keep a cookie cutter that you never use. It takes up space and you waste time cleaning around it (or not, in which case I hope I never see what else you have in that junk drawer); time that could be spent talking about or to your grandma. If your grandma's anything like mine she would sternly scold you for wasting time not talking to her.
Maybe my rant has yet to convince you. Think of it in these terms: photo albums are nice, those letters you passed back and forth in class - so cute, yearbooks from first grade - even cuter; but do you look at these things? Do you take them out and have a feel good moment with your bottle of wine, and one or two friends with nothing better to do on their Saturday night? Or have they been sitting untouched in your parent's basement for uncounted years, only to continue to do so for eternity?
If you don't use it - lose it, you won't lose those memories.