@Abeline, that is a tough emotional hit, especially for someone who is using all her emotional and physical energy trying to unclutter. I actually get a little backhanded guilt when I do it - I hear "Well, that's great that you did that, but what about all the crap in your..." Ugh. Like I'm not trying hard enough already!
Don't feel alone, all of us have some one person who will probably be a little hurt by some one of the things that goes. We like to say that they'll never know, but i think @inga and @badkitti's response - a happy future, or like in the book, room to begin a new chapter - is what you are really trying to achieve.
Is there anything you two would like to do together - have friends or family come to visit more often, expand the family, invest in major piece of furniture for your home (not a clutter, but a keeper and good investment), or be more social. That last one is a big motivation for us - we never have people over because it's just too much effort to get "straightened" much less all the entertaining work. That holds us back socially, not just in terms of what we're doing on a Friday night. Whatever the reason, maybe that can be your guiding force if he also wants to do that
On the mix tapes, I am *right* there with you. It must be our age? So, I know your post was more about the emotional block there but here is a bit on the actual tape dilemma.
I have a BIG tape box (I mean holds 100 tapes, double sided!) full of mix tapes, some date to high school, but one whole side is from my now husband and I back and forth to each other. We made these adorable cases with collages or pictures or our own messages. I love what they mean to me - except that in reality they are this giant block of unnecessary stuff. I don't even think we HAVE a tape player in the house anymore!
Here's what I'm mid-process in doing -
1) I took digital photographs or scanned any of the cases that mean anything to me. We have a two-box cassette tape set that we made, His: Can't Help Falling, Mine: In Love With You - sigh, I have to keep those memories but an image will do it. I'm looking into some fun ways to "keepsake" them (I have another post about that for my kids' art - a photo book might be a nice way b/c there are all there together.
2) A bit time consuming, but great TV time - I took a spreadsheet (or just a document will work) and typed in the cassette tape tracks. Then, I'm making them into iTunes Playlists. MOST of the music, we do actually own because we've loved it and bought it along the way on CD or digitally already. But, some I don't and I'll just keep the file and eventually maybe decide to add it to my owned music. Wouldn't it be nicer to be able to LISTEN to the music you loved together or he created in a mix for you? Play it from iTunes in your house, on your iPod or burn a DVD (which you can do forever, once it's digital).
3) The services @badkitti mentions are out there - and there are some that you can send them a tape or a local business (often photography store) does it for you. I have ONE tape that I sent him while he was in a job that took him traveling away from me a whole summer. I recorded my voice talking to him on the tape - and (whew) while I wince at some of what I said and how silly I sound, that's one that I want to have the audio file for digitally.
Hope that helps! Keep your chin up -