Deciding what to sell?

So here's a question for those who sell their clothes- what goes into your decision to do so? How do you choose which items stay and which go? If a new item is released you absolutely adore do you sift through your current closet and choose something to go even if you still like your old item? Or do you only sell your clothes for absolute emergencies? Or only when you genuinely don't wear them anymore? I'm curious how many Lolitas have sold off a majority of their closet in order to fund a new style, either a new Lolita substyle or new style of clothing altogether, or how many have sold off all their cheaper purchases to replace them with only brand.

I'm curious to read others' experiences and opinions! :) Especially from the recent onslaught of beautiful closets from January I'm going through and picking and choosing from my own wardrobe now for what really needs to stay and go and I have to say, I'm running into conflicts.