I am so sentimental I can't stand it! I also am somewhat of a neat freak. So, several years ago, I started organizing all of the stuff I couldn't part with. I keep my very favorite clothes from each child in their own storage container. Each year on Jan 1, we start a new box of family memories. Anything that comes along that year that is worthy of keeping and remembering, gets tossed into the box - letters, tickets, pictures, surprises we received, etc. On New Year's eve, 364 days later, we go through the old boxes sometimes to remember all the fun times we've shared.
I also keep a box each year for each child in which goes their own specific things I want to keep - school stuff, poems they've written me, etc. I also used to write a journal each year for each child recalling all the memories as they happened and put it in their box. But there were a couple of years where I wasn't so good at keeping up with the journals - and now I do blogs instead of journals.
Sometimes I go back and look through a box from the toddler years and read the journal I wrote and just cry! I am soooo glad I wrote down all the the cute little things that they did. You think you will remember it all - but sometimes I read things that I have forgotten about- and it's so sweet. I feel a little guilty for missing those couple of years when I didn't do it. Wish I had done it, now.
I have a 10, 8, and 2 year old now, and it just goes by so fast! How I wish I could travel back in time sometimes to see them as babies again!
Changing out clothes each year is always a painful experience - marks the passage of time and how much they're growing!
I try to enjoy the here and now while it is still here!
Tomorrow it will be in a memory box.
I read in a book recently to cherish all the moments you can with your 10-11 year old while there is still that "great closeness and unpretentious love" betweeen you and your child. Makes me just want to hug my 10 year old all day long while she still lets me!
I am good about getting rid of some "stuff" but not others. I pass on DD's clothes to my 3 nieces so that helps; had DS's clothes from birth up in our attic until he was 10 and we were moving. I just tell myself that they ended up with someone who needed them more than our storage space. I did keep a few special clothing items. But I have bins and scrap books/photo albums that contain movie stubs, report cards, special art work, birthday invites, etc. for each of them (even some from when I was growing up). I figure that since I think these are special items, I'll leave it up to them when they grow up and have their own homes, to decide whether to keep it or toss (they just can't tell me if they get rid of it or I might take it all back 
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