We already get 25 storage spaces for each part of our armour (easily enough for something different for every job) and 4 pages of inventory too (100 items).

Then if you've got far enough in the main story (a few hours work?) we also get two retainers, each of whom can store 175 items.

Then there's the armoire in our room which isn't overly helpful, but it can store the majority of stuff which is one time only and you don't want/can't discard it.

I used to hoard everything as well, but then realised that's really pointless and sold it on the auction houses, for pretty much pennies. Which also means if I want those items back again later, there won't really be much problem buying them back and they won't cost me a huge amount to do so either.

Keep your inventory slots for green/pinks or things you're crafting with right now. Anything else, sell/convert/discard.