I used to collect Art Nouveau and Arts & Crafts Movement furniture/decorative items. This eventually became an obsession with anything remotely connected - so cushions/curtains/bedding, artwork, rugs...even the loo roll holders! - till everything in our house was on that theme.
I loved it all, but it was way too much. People commented that our house resembled a museum. When we began downsizing a few years back, lots had to go including my prized possession, a fabulous Liberty sideboard believed to be a one-off, exhibition piece.
We still have fourteen (smaller) pieces of Art Nouveau/Arts & Crafts furniture, a few decorative bits (mirrors, busts etc) and my collection of Bretby jewelware pottery (23 vases/jugs), which I have no plan to part with even though my style is now much more eclectic.
The other things I collect are books (I have around 100 on the subject of Art Nouveau/Arts & Crafts Movement/Pre-raphaelite art) and framed taxidermy butterflies.
Tbh, our home still resembles a museum - but a more jumbled one these days!