It is so hard, isn't it ? I deal with this too, and some days it drags me down so much. I have been determinedly decluttering my stuff (and the kids') for months now, but pretty much every week dh brings in more junk (thanks to yard sales, estate sales, alley shopping, etc etc), and this is with an enormous collection of crap already clogging the house. I also love saleing, but I'm discriminating about what I will buy/allow into the house - and I've encouraged him to also look at things with a careful eye (need it ? love it ? can't live without it ? okay - but nothing that doesn't meet that criteria). Unfortunately, this is a man that can love any straggly piece of trash, so it all seems to come in.
The only thing that seemed to have any effect is when I took him on a tour of the storage areas of our house, and pointed out that he dominates all of these spaces with his stuff. There are 5 people in this house, and one of them hogs all of the storage. The inequity there seemed to have some effect, and he began packing up a bunch of storage boxes with his stuff and moving it to the garage (which is already jam packed - all his stuff).
Part of me admires that he can see potential/use/function/etc in pretty much anything. But mostly I just feel like all the stuff - the junk & clutter (and did I mention the 40+ chairs in our 1600sq foot house) is driving me batty.