hi a girl, i've been through this, and it does get better. a good sense of humor is very important.
i also had box issues. my x moved out but hadn't taken her boxes from the attic. took her 2 years, and lots of "i'll come get them next weeks" until she finally did.
and i felt a big difference afterwards. as if, now it was my place and she has no reason to come in. (and that was the last time she actually came in)
since then i've gone around my place and felt out all the areas that still give off negative vibes, that still had bad memories, and painted, replaced, moved and re-arranged until its now much more just mine.
the more ways you can clean out the negative, both physically and emotionally, the better you'll feel. boxing his things is an act of healing.
"In a ham and eggs breakfast, the hen is involved, but the pig is committed".