|Too much of a good thing.|
If your collections are random or disorganized, they are not ready for display. Keep with themes that people can comprehend and enjoy.
If you're drawn to garage sale items "just because," or you collect things for undefined "later" use, then you may be leaning towards hoarding, and you've got to try to control that in the interest of fighting clutter. Is it "OPJ"- other people's junk? If so, let them handle it by donating or disposing of it before you take ownership just to drop it on a pile in your garage or basement.
Finally, to your friends who give you cat-themed items because at one time or another you mentioned that you like cats, it's perfectly fine between gift-giving seasons to say (as sweetly as possible) that you've changed, and that cat items aren't your thing anymore. And, when you think about it, you have changed! --You're not into clutter any more! Congratulations!