^ I used to do that too, and for me, I think it was bad

I guess it depends whether you have variety in your wardrobe, and whether you have something to wear on all occasions ... or if your wardrobe is "heavy" in certain areas. To me this is where a plan comes in handy ...
I remember my great-aunt showing me--many years ago now, she was in her 70s or possibly 80s at the time--a cup and saucer, and wistfully telling me that it was the china pattern she wanted to buy, but her husband had this one in, one out rule ...
They paid cash for everything, so what this meant was she had cash in hand to buy what she really, really wanted (and would remember wanting decades later), but she couldn't because she didn't have things that she could get rid of to bring the china in.
At that point, you are no longer in charge of your life--the stuff is. Things are here for us to enjoy, and we should do it. At that moment I was very unhappy with my great-uncle and his one in, one out rule, and I have yet to change my mind.
If something needs to go, it needs to go whether or not you're bringing something new in. If you really want to bring something new in, you should do so whether you have something that should leave or not.
Personally I like to clear out at the end of a season. I may make a decision earlier that it will go at the end of the season, but sometimes if you get rid of something at the wrong point in time, you still need it, but it can literally be impossible to replace due to what merchandise is in the stores at that time. This is especially true if you live in a climate with unbalanced seasons, i.e., the vast majority of the year is either summer-like or winter-like. If the whole country is like that, the problem may not exist, but here, where we have such a variety of climates, the fashion calendar rules. So I'll shop for a replacement at the beginning of the same season the following year.