HA! I kept some of my sentimental possessions. They survived one of our houses burning down. And we laid out the 40 ft bus interior around them. I kept the round topped cedar chest David built me for my wedding present 34 years ago. I kept the cannonball 4 poster waterbed frame we bought to replace the one that burned up in the fire. We did have to cut the frame down from a king to a full. I kept my 30" LP range (bakes better than any other I've had), kept my Aladdin mantle lamp, kept a tiny glass topped rock maple end table bought from a thrift store (age unknown), kept a Schwartz key wind anniversary clock my Dad (RIP) gave me that he brought back from when he was stationed in Germany, my "collection" of three ceramic beer steins, the two crystal wine glasses we toasted with at our wedding, an oil painting and a lithograph (low numbers and the artist signed it right in front of me at a state park) and a 1926 Craftsman mantle (shortened and narrowed to fit in the bus) to remind us to never trust outsiders again. NO ONE has any business telling you that you should get rid of any thing with sentimental value. NO ONE has any business telling you what to get rid of. Only you can make those decisions. You may want to put some of your stuff into a small storage unit (you can get some pretty small ones), until you either feel you can let it go or you can find a place for it or you decide you can't live without it and you need a bigger place to live.
Clothing can be replaced seasonally at thrift stores. That said, I have a nice convertable coat from LL Bean that I keep. David has a heavy winter coat that we store in the cedar chest that I wore several times during the winter. Who here wants to explain to my kids that we got rid of the coat they bought him with the money they earned as teens working construction? Any fool who wants that job had better be able to duck fast and run faster! I currently have 3 rather large quilts (and we use them all) stored for the summer in my cedar chest. One is still on the bed. Putting stuff in storage will cost you. But it will help you weed out what you REALLY want to keep. I kept a lot of stuff that has been used to stock the bus with. Some of the stuff simply can't be replaced. My old Griswold cast iron skillet was bought at a flea market 35 years ago, beautifully seasoned and priceless to me. It's also heavy and many have said I need to get rid of it (nope, we use it, used it tent camping, in homes, in the popup and use it now).
Use what others say as a guideline but don't just toss everything. You may decide that living in a van is not for you. That could happen in a month or a year. Yes, I know that statement is heresy on this forum but it is something to consider. Living in a tiny van is not for everyone. It certainly isn't for us. Find a centrally located storage unit to where you will be traveling and put your stuff there. I once met some folks who would stop and change out their stuff seasonally. They worked and traveled (NOT work kamping either, you can work at anyplace for more money). We have had to maintain storage units for up to two years at times (we moved a lot and tended to buy or rent houses until we got smart and went with an RV). No my stuff couldn't just be "replaced" as I had a lot of "neartiques".
BTW, I go to pick up my late 1800's rocking chair this coming weekend. It will be re-glued, reupholstered and be put in the bus. I now only have the three "neartiques" (mantle, table and rocking chair). I love these things, they are beautiful and while I wouldn't risk my life for them, I did plan carefully to put them in the bus. As to anyone who thinks I should get rid of them or anything else I have kept, I say that's is their opinion and their opinion does not count. One thing to remember is that while material possessions should not own you, nor should you be too concerned over others opinions. The people who are so fast to tell you to junk it all did not get to that point overnight. Plus I'm sure they have stuff that you would think they should toss, yet they think they need to keep their "necessary" stuff. You will change your outlook on some of your stuff, others you won't. After many years, I have given up almost all of my books (not my leather bound ones) and I now have a used $35 kindle ereader (I can read it out in the sun) and get freebie books off of amazon daily. I have bought a few as well. I still love reading a well printed book on good paper. I have my leather bound books for that. You learn that you can change what stuff you think you can't part with.